求调，20pts

#include<bits/stdc++.h>
#define int long long
using namespace std;
typedef long long ll;
const int N =1e6+5,inf = 2e9,memse = 0x3f;
using pii = pair<int,int>;
struct TreeNode
{
	int l,r;
	ll mx;
	void tag(ll x){
		mx =x; 
	}  
};
int a[N],nfd[N];//nfd[i]: dfn为i值的点
struct SegTree
{
	#define ls num<<1
	#define rs num<<1|1
	#define mid ((tr[num].l+tr[num].r)>>1)
	TreeNode tr[N<<2];
	void Up(TreeNode &a,TreeNode b, TreeNode c){
		a.mx= max(b.mx , c.mx);
	} 
	
	void build(int num,int L,int R){
		tr[num].l=L,tr[num].r=R;
		if(L==R){
			tr[num].mx = a[nfd[L]];
			return;
		}
		build(ls,L,mid);
		build(rs,mid+1,R);
		Up(tr[num],tr[ls],tr[rs]);
	}
	void upd(int num, int tar, ll v)
	{
		if (tr[num].l==tr[num].r&&tr[num].l == tar)
		{
			tr[num].tag(v);
			return;
		}
		if (mid >= tar)
			upd(ls, tar, v);
		else
			upd(rs, tar, v);
		Up(tr[num], tr[ls], tr[rs]);
	}
		
	TreeNode qry(int num,int L,int R){
		if(L<=tr[num].l&&tr[num].r<=R){
			return tr[num];
		}
		TreeNode x={0,0,0};
		if(L<=mid) Up(x,x,qry(ls,L,R));
		if(mid<R) Up(x,x,qry(rs,L,R));
		return x;
	}
}tree;

struct Edge{int to,nxt,val,id=-1;}e[N<<2];int head[N],Ecnt;
void add(int u,int v,int w){e[++Ecnt] = {v,head[u],w};head[u] = Ecnt;}
int sz[N],dep[N],fa[N],son[N];
int top[N],dfn[N],tim;

void dfs1(int u,int fat){
	
	sz[u]=1,fa[u]=fat,dep[u]=dep[fat]+1;
	for(int i=head[u];i;i=e[i].nxt){
		int v=e[i].to; 
		if(v==fat) continue;
		a[v]=e[i].val;
		e[i].id=v;
		dfs1(v,u);
		sz[u] += sz[v];
		if(sz[v] > sz[son[u]]) son[u] = v;
	}
}
void dfs2(int u,int tp ){
	dfn[u]=++tim,nfd[tim]=u,top[u]=tp;
	if(son[u]) dfs2(son[u],tp);
	for(int i=head[u];i;i=e[i].nxt){
		int v=e[i].to;
		if(v==fa[u]||v==son[u]) continue;
		dfs2(v,v);
	}
}
ll qry_pth(int u,int v){
	ll res =0;
	while(top[u] != top[v]){
		if(dep[top[u]]<dep[top[v]]) swap(u,v);
		res = max(res,tree.qry(1,dfn[top[u]],dfn[u]).mx);
		u = fa[top[u]];
	}
	if(dep[u]<dep[v]) swap(u,v);
	res=max(res,tree.qry(1,dfn[v],dfn[u]).mx);
	return res;
}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	//求助，树剖20pts，把边权下放到点上去了。
	int n;
	cin>>n;
	for(int i=1;i<n;i++){
		int u,v,w;
		cin>>u>>v>>w;
		add(u,v,w);
		add(v,u,w);
	}
	dfs1(1,0);
	dfs2(1,1);
	tree.build(1,1,n);
	string opt;
	while(cin>>opt){
		if(opt=="DONE") break;
		int x,y;cin>>x>>y;
		if(opt=="QUERY") cout<< qry_pth(x,y)<<'\n';
		else tree.upd(1,dfn[e[2*(x-1)+1].id],y);
	}
	return 0;
}