玄关，求调,40pts WA

#include<bits/stdc++.h>
#define fi first
#define se second
using namespace std;
const int N = 3e5 + 5;

int n;

vector <pair<int,pair<int,int> > > e[N];

int fa[N], dep[N], top[N], son[N], siz[N], rnk[N], dfn[N], d[N], p[N];

int cnt;

void dfs1(int x,int f) {
    siz[x] = 1;
    for(auto v : e[x]) {
        if(v.fi==f) continue;
        dfn[v.fi] = ++cnt;
        rnk[cnt] = v.fi;
        p[v.se.se] = cnt;
        fa[v.fi] = x;
        dep[v.fi] = dep[x] + 1;
        d[v.fi] = v.se.fi;
        dfs1(v.fi,x);
        siz[x] += siz[v.fi];
        if(siz[v.fi] > siz[son[x]]) son[x] = v.fi;
    }
    return ;
}

void dfs2(int x,int tp) {
    top[x] = tp;
    for(auto v : e[x]) {
        if(v.fi==fa[x]) continue;
        if(v.fi==son[x]) dfs2(v.fi,tp);
        else dfs2(v.fi,v.fi);
    }
    return ;
}

struct xds_Tree {
    int tree[N];
    #define mid (l+r>>1)
    #define ls (x<<1)
    #define rs (x<<1|1)
    void pushup(int x) {
        return void(tree[x] = max(tree[ls], tree[rs]));
    }
    void build(int x,int l,int r) {
        if(l==r) return void(tree[x] = d[rnk[l]]);
        build(ls,l,mid), build(rs,mid+1,r);
        return void(pushup(x));
    }
    void update(int x,int l,int r,int L,int d) {
        if(l==r&&L==l) return void(tree[x] = d);
        if(L<=mid) update(ls,l,mid,L,d);
        else update(rs,mid+1,r,L,d);
        return void(pushup(x));
    }
    int query(int x,int y) {
        int res = 0;
        while(top[x]!=top[y]) {
            if(dep[top[x]] < dep[top[y]]) swap(x,y);
            res = max(res,Query(1,1,n,dfn[top[x]],dfn[x]));
            x = fa[top[x]];
        }
        if(dfn[x] > dfn[y]) swap(x,y);
        res = max(res,Query(1,1,n,dfn[x]+1,dfn[y]));
        return res;
    }
    int Query(int x,int l,int r,int L,int R) {
        if(l>=L&&r<=R) return tree[x];
        int res = 0;
        if(L<=mid) res = Query(ls,l,mid,L,R);
        if(R>mid) res = max(res,Query(rs,mid+1,r,L,R));
        return res;
    }
}T;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    cin>>n;
    int u, v, w;
    for(int i=1; i<n; ++i) {
        cin>>u>>v>>w;
        e[u].push_back({v,{w,i}});
        e[v].push_back({u,{w,i}});
    }
    dfn[1] = ++cnt;
    dfs1(1,1);
    dfs2(1,1);
    T.build(1,1,n);
    string opt;
    int x, y;
    while(1) {
        cin>>opt;
        if(opt=="DONE") break;
        else if(opt=="QUERY") {
            cin>>x>>y;
            if(x==y) cout<<0<<"\n"; 
            else cout<<T.query(x,y)<<"\n";
        } else {
            cin>>x>>y;
            T.update(1,1,n,p[x],y);
        }
    }
    return 0;
}