WA 0求调

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned ll
#define ui unsigned int
#define i128 __int128
#define mems(x, y) memset((x), (y), sizeof (x))
#define lid (id << 1)
#define rid (id << 1 | 1)
#define pc(x) __builtin_popcount(x)
#define pcll(x) __builtin_popcountll(x)
#define De(x) cout << #x << ": " << x << '\n'
#define DE(x) cout << #x << ": " << x << ' '
const int N = 5e5+5;
const int intmin = -0x3f3f3f3f, intmax = 0x3f3f3f3f;
const ll llmin = -0x3f3f3f3f3f3f3f3f, llmax = 0x3f3f3f3f3f3f3f3f;
#ifdef ONLINE_JUDGE
#define cin IO::InputHelper::get_instance()
#define cout IO::OutputHelper::get_instance()
#define INPUT_FILE ""
#define OUTPUT_FILE ""
namespace IO {
    using size_type = size_t;
    static constexpr size_type INPUT_BUFFER_SIZE = 1 << 16, OUTPUT_BUFFER_SIZE = 1 << 16, MAX_INTEGER_SIZE = 20, MAX_FLOAT_SIZE = 50;static constexpr char input_file[] = INPUT_FILE, output_file[] = OUTPUT_FILE;
    struct InputHelper {
        FILE *m_file_ptr;char m_buf[INPUT_BUFFER_SIZE], *m_end, *m_cursor;bool m_ok;
        InputHelper &set_bad() { return m_ok = false, *this; }
        template <size_type BlockSize>
        void _reserve() {size_type a = m_end - m_cursor;if (a >= BlockSize) return;memmove(m_buf, m_cursor, a), m_cursor = m_buf;size_type b = a + fread(m_buf + a, 1, INPUT_BUFFER_SIZE - a, m_file_ptr);if (b < INPUT_BUFFER_SIZE) m_end = m_buf + b, *m_end = EOF;}
        template <typename Tp, typename BinaryOperation>
        InputHelper &fill_integer(Tp &ret, BinaryOperation op) {if (!isdigit(*m_cursor)) return set_bad();ret = op(Tp(0), *m_cursor - '0');size_type len = 1;while (isdigit(*(m_cursor + len))) ret = op(ret * 10, *(m_cursor + len++) - '0');m_cursor += len;return *this;}
        explicit InputHelper(const char *inputFileName) : m_ok(true), m_cursor(m_buf + INPUT_BUFFER_SIZE), m_end(m_buf + INPUT_BUFFER_SIZE) { m_file_ptr = *inputFileName ? fopen(inputFileName, "rt") : stdin; }
        ~InputHelper() { fclose(m_file_ptr); }
        static InputHelper &get_instance() {static InputHelper s_obj(input_file);return s_obj;}
        static bool is_blank(char c) { return c == ' ' || c == '\t' || c == '\n' || c == '\r'; }static bool is_endline(char c) { return c == '\n' || c == EOF; }
        const char &getchar_checked() {_reserve<1>();return *m_cursor;}const char &getchar_unchecked() const { return *m_cursor; }
        void next() { ++m_cursor; }
        template <typename Tp, typename std::enable_if<std::is_signed<Tp>::value & std::is_integral<Tp>::value>::type * = nullptr>
        InputHelper &operator>>(Tp &num) {while (is_blank(getchar_checked())) next();_reserve<MAX_INTEGER_SIZE>();if (getchar_unchecked() != '-') return fill_integer(num, std::plus<Tp>());next();return fill_integer(num, std::minus<Tp>());}
        template <typename Tp, typename std::enable_if<std::is_unsigned<Tp>::value & std::is_integral<Tp>::value>::type * = nullptr>
        InputHelper &operator>>(Tp &num) {while (is_blank(getchar_checked())) next();_reserve<MAX_INTEGER_SIZE>();return fill_integer(num, std::plus<Tp>());}
        template <typename Tp, typename std::enable_if<std::is_floating_point<Tp>::value>::type * = nullptr>
        InputHelper &operator>>(Tp &num) {
            bool neg = false, integer = false, decimal = false;while (is_blank(getchar_checked())) next();_reserve<MAX_FLOAT_SIZE>();
            if (getchar_unchecked() == '-') {neg = true;next();}if (!isdigit(getchar_unchecked()) && getchar_unchecked() != '.') return set_bad();
            if (isdigit(getchar_unchecked())) {integer = true;num = getchar_unchecked() - '0';while (next(), isdigit(getchar_unchecked())) num = num * 10 + (getchar_unchecked() - '0');}
            if (getchar_unchecked() == '.') if (next(), isdigit(getchar_unchecked())) {if (!integer) num = 0;decimal = true;Tp unit = 0.1;num += unit * (getchar_unchecked() - '0');while (next(), isdigit(getchar_unchecked())) num += (unit *= 0.1) * (getchar_unchecked() - '0');}
            if (!integer && !decimal) return set_bad();if (neg) num = -num;return *this;
        }
        InputHelper &operator>>(char &c) {while (is_blank(getchar_checked())) next();if (getchar_checked() == EOF) return set_bad();c = getchar_checked(), next();return *this;}
        InputHelper &operator>>(std::string &s) {while (is_blank(getchar_checked())) next();if (getchar_checked() == EOF) return set_bad();s.clear();do {s += getchar_checked();next();} while (!is_blank(getchar_checked()) && getchar_unchecked() != EOF);return *this;}
        explicit operator bool() { return m_ok; }
    };
    struct OutputHelper {
        FILE *m_file_ptr = nullptr;char m_buf[OUTPUT_BUFFER_SIZE], *m_end, *m_cursor;char m_temp_buf[MAX_FLOAT_SIZE], *m_temp_buf_cursor, *m_temp_buf_dot;uint64_t m_float_reserve, m_float_ratio;
        void _write() { fwrite(m_buf, 1, m_cursor - m_buf, m_file_ptr), m_cursor = m_buf; }
        template <size_type BlockSize> void _reserve() {size_type a = m_end - m_cursor;if (a >= BlockSize) return;_write();}
        OutputHelper(const char *outputFileName, size_type prec = 6) : m_cursor(m_buf), m_end(m_buf + OUTPUT_BUFFER_SIZE), m_temp_buf_cursor(m_temp_buf) { m_file_ptr = *outputFileName ? fopen(outputFileName, "wt") : stdout, precision(prec); }
        static OutputHelper &get_instance() {static OutputHelper s_obj(output_file);return s_obj;}
        ~OutputHelper() { flush(), fclose(m_file_ptr); }
        void precision(size_type prec) { m_float_reserve = prec, m_float_ratio = uint64_t(std::pow(10, prec)), m_temp_buf_dot = m_temp_buf + prec; }
        OutputHelper &flush() { return _write(), fflush(m_file_ptr), *this; }
        void putchar(const char &c) {if (m_cursor == m_end) _write();*m_cursor++ = c;}
        template <typename Tp, typename std::enable_if<std::is_signed<Tp>::value & std::is_integral<Tp>::value>::type * = nullptr>
        OutputHelper &operator<<(Tp ret) {_reserve<MAX_INTEGER_SIZE>();size_type len = 0;if (ret >= 0) do *(m_cursor + len++) = '0' + ret % 10, ret /= 10;while (ret);else {putchar('-');do *(m_cursor + len++) = '0' - ret % 10, ret /= 10;while (ret);}for (size_type i = 0, j = len - 1; i < j;) std::swap(*(m_cursor + i++), *(m_cursor + j--));m_cursor += len;return *this;}
        template <typename Tp, typename std::enable_if<std::is_unsigned<Tp>::value & std::is_integral<Tp>::value>::type * = nullptr>
        OutputHelper &operator<<(Tp ret) {_reserve<MAX_INTEGER_SIZE>();size_type len = 0;do *(m_cursor + len++) = '0' + ret % 10, ret /= 10;while (ret);for (size_type i = 0, j = len - 1; i < j;) std::swap(*(m_cursor + i++), *(m_cursor + j--));m_cursor += len;return *this;}
        template <typename Tp, typename std::enable_if<std::is_floating_point<Tp>::value>::type * = nullptr>
        OutputHelper &operator<<(Tp ret) {
            if (ret < 0) {putchar('-');return *this << -ret;}ret *= m_float_ratio;uint64_t integer = ret;if (ret - integer >= 0.4999999999) integer++;do {*m_temp_buf_cursor++ = '0' + integer % 10;integer /= 10;} while (integer);
            if (m_temp_buf_cursor > m_temp_buf_dot) {do putchar(*--m_temp_buf_cursor);while (m_temp_buf_cursor > m_temp_buf_dot);putchar('.');}else {putchar('0'), putchar('.');for (size_type i = m_temp_buf_dot - m_temp_buf_cursor; i--;) putchar('0');}
            do putchar(*--m_temp_buf_cursor);while (m_temp_buf_cursor > m_temp_buf);
            return *this;
        }
        OutputHelper &operator<<(const char &ret) {putchar(ret);return *this;}
        OutputHelper &operator<<(const char *ret) {while (*ret) putchar(*ret++);return *this;}
        OutputHelper &operator<<(const std::string &ret) { return *this << ret.data(); }
    };
    InputHelper &getline(InputHelper &ih, std::string &line) {line.clear();if (ih.getchar_checked() == EOF) return ih.set_bad();while (!InputHelper::is_endline(ih.getchar_checked())) line += ih.getchar_unchecked(), ih.next();if (ih.getchar_unchecked() != EOF) ih.next();return ih;}
}using IO::getline;
#endif
namespace funcqwq{
    mt19937 rd(time(0));
    inline ll qpow(ll a, ll b){ll res = 1;for (;b;a *= a, b >>= 1)if (b & 1)res = res * a;return res;}
    inline ll qpow(ll a, ll b,  ll p){ll res = 1;for (;b;a = (i128)a * a % p,b >>= 1){(b & 1 ? res = (i128)res * a % p : 0);}return res;}
    inline ll _gcd(ll a, ll b){if (!a || !b) return a | b;int t = __builtin_ctzll(a | b);a >>= __builtin_ctzll(a);do{b >>= __builtin_ctzll(b);if (b < a) swap(a, b);b -= a;}while(b);return a << t;}
    inline ll llrd(){return (rd() << 10) ^ ((rd() ^ 0x28208a20a08a28ac));}
    inline int intrd(){return ((rd() >> 2) ^ 0x12345678);}
    bool miller_rabin(const ll p){
        if (p < 64) return 0x28208a20a08a28ac >> p & 1;if (!(p % 2)||!(p % 3)||!(p % 5)||!(p % 7)) return 0;
        ll d = p - 1;short k = __builtin_ctzll(d);d >>= k;
        for (register short asd = 0;8 - asd;++asd){
            ll pw = qpow(llrd()%(p-1)+1,d,p),pw1;
            for (register short j = 0;k - j;++j){pw1=(i128)pw*pw%p;if(pw1==1&&(pw^1)&&(pw^(p - 1)))return 0;pw = pw1;}
            if (pw ^ 1) return 0;
        }
        return 1;
    }
    namespace PRqwq{
        inline ll PR(ll x){
            if (x == 4) return 2;
            ll c= llrd() % (x - 2) + 1;ll s = llrd() % (x - 2) + 1, t = s;
            s = (i128)(s * s + c) % x;t = (i128)(t * t + c) % x;t = ((i128)t * t + c) % x;
            for (short i = 1;s ^ t;i = min(128, i << 1)){
                ll sum = 1, sum1;
                for (short j = 0;i - j;++j){
                    if (!(sum1 = (i128)sum * abs(t - s) % x)) break;
                    sum = sum1;s = ((i128)s * s + c) % x;t = ((i128)t * t + c) % x;t = ((i128)t * t + c) % x;
                }
                if ((sum1 = _gcd(sum, x)) ^ 1) return sum1;
            }
            return x;
        }
        ll mxfc;
        vector<pair<ll, short> > fc;
        inline void maxfac(ll x){if (x<2||x<=mxfc)return;if(miller_rabin(x))return(mxfc<x?mxfc=x:0),void();ll tmp=x;while(tmp>=x)tmp=PR(tmp);while(!(x%tmp))x/=tmp;maxfac(x),maxfac(tmp);}
        inline ll max_fac(ll x){mxfc = 1;maxfac(x);return mxfc;}
        inline void getfac(ll x){if(x==1)return;mxfc=1;maxfac(x);if(mxfc==x)return fc.emplace_back(mxfc,1),void();else{short c=0;while(!(x%mxfc))x/=mxfc,++c;fc.emplace_back(mxfc,c);getfac(x);}}
        inline vector<pair<ll, short> > get_fac(ll x, bool op = 0){fc.clear();getfac(x);if(op)reverse(fc.begin(),fc.end());return fc;}
    }
    using PRqwq::max_fac;
    using PRqwq::get_fac;
}
using funcqwq::qpow;
using funcqwq::miller_rabin;
using funcqwq::_gcd;
using funcqwq::max_fac;
using funcqwq::llrd;
using funcqwq::get_fac;
using funcqwq::intrd;
namespace tianyu{
    int n, m;
    vector<pair<int, int> > G[N];
    bool gb[4000010];
    int dfn[N], low[N], tot;
    void tarjan(int u, int f){
        dfn[u] = low[u] = ++tot;
        for (auto i : G[u]){
            int v = i.first;
            if (v == f) continue;
            if (!dfn[u]){
                tarjan(v, u);
                low[u] = min(low[u], low[v]);
                if (low[v] > dfn[u]) gb[i.second] = gb[i.second ^ 1] = 1;
            }
            else{
                low[u] = min(low[u], dfn[v]);
            }
        }
    }
    bool vis[N];
    vector<int> ans[N];
    int cnt;
    void dfs(int u){
        ans[cnt].emplace_back(u);
        vis[u] = 1;
        for (auto i : G[u]){
            int v = i.first;
            if (gb[i.second] || vis[v]) continue;
            dfs(v);
        }
    }
    void awa(){
        cin >> n >> m;
        for (int i = 1;i <= m;i++){
            int u, v;
            cin >> u >> v;
            G[u].emplace_back(v, i << 1);
            G[v].emplace_back(u, i << 1 | 1);
        }
        for (int i = 1;i <= n;i++) if (!dfn[i]) tarjan(i, 0);
        for (int i = 1;i <= n;i++) if (!vis[i]) ++cnt, dfs(i);
        cout << cnt << '\n';
        for (int i = 1;i <= cnt;i++){
            cout << ans[i].size() << ' ';
            for (int j : ans[i]) cout << j << ' ';
            cout << '\n';
        }
    }
}
signed main(){
    int T = 1;
    while (T--) tianyu::awa();
    return 0;
}