蜜汁MLE？？？

rt，写的主席树，没觉得会爆空间啊

#include <bits/stdc++.h>
using namespace std;

namespace IO {
    #define gc getchar
    #define int long long
    const int N = 3e5+10;
    const int INF = ~0U>>1;
    template <typename T>
    inline void read(T &x) {
        x = 0; T flag = 1;
        char c = gc();
        for(; !isdigit(c); c = gc()) if(c == '-') flag = -1;
        for(; isdigit(c); c = gc()) x = (x<<3) + (x<<1) + (c^48);
        x *= flag;
    } 
    template <typename T, typename ...Args>
    inline void read(T &x, Args &...args) {
        read(x); read(args...);
    }
    #undef gc
} using namespace IO;

int n, q;
vector<int> G[N];
int dep[N], siz[N], dfn[N], DFN, maxdep = 1;
int L[N*20], R[N*20], sum[N*20], root[N], cnt;

namespace HJT {
    int build(int l, int r) {
        int p = ++cnt;
        sum[p] = 0;
        if(l < r) {
            int mid = (l+r)>>1;
            L[p] = build(l, mid);
            R[p] = build(mid+1, r);
        }
        return p;
    }

    int insert(int old, int l, int r, int val, int pos) {
        int p = ++cnt;
        L[p] = L[old], R[p] = R[old], sum[p] = sum[old]+val;
        if(l < r) {
            int mid = (l+r)>>1;
            if(pos <= mid) L[p] = insert(L[old], l, mid, val, pos);
            else R[p] = insert(R[old], mid+1, r, val, pos);
        }
        return p;
    }

    int query(int x, int y, int l, int r, int dl, int dr) {
        if(l == dl && r == dr) return sum[y] - sum[x];
        int mid = (l+r)>>1, res = 0;
        if(dl <= mid) res += query(L[x], L[y], l, mid, dl, dr);
        if(dr > mid) res += query(R[x], R[y], mid+1, r, dl, dr);
        return res;
    }
}

void dfs1(int x) {
    siz[x] = 1;
    for(int i = 0; i < G[x].size(); i++) {
        int y = G[x][i];
        if(dep[y]) continue;
        dep[y] = dep[x]+1;
        maxdep = max(maxdep, dep[y]);
        dfs1(y);
        siz[x] += siz[y];
    }
}

void dfs2(int x) {
    dfn[x] = ++DFN;
    root[DFN] = HJT::insert(root[DFN-1], 1, maxdep, siz[x]-1, dep[x]);
    for(int i = 0; i < G[x].size(); i++) {
        int y = G[x][i];
        if(dep[y] < dep[x]) continue;
        dfs2(y);
    }
}

signed main() {
    read(n, q);
    for(int i = 1, x, y; i < n; i++) read(x, y), G[x].push_back(y), G[y].push_back(x);
    dep[1] = 1;
    dfs1(1);
    HJT::build(1, maxdep);
    dfs2(1);
    while(q--) {
        int p, k, ans;
        read(p, k);
        ans = (siz[p]-1)*min(dep[p]-1, k);
        ans += HJT::query(root[dfn[p]-1], root[dfn[p]+siz[p]-1], 1, maxdep, dep[p]+1, min(maxdep, dep[p]+k));
        printf("%lld\n", ans);
    }
    return 0;
}