$70$ 分，其他 WA。

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <vector>
#include <string>
using namespace std;

const int N = 1e5 + 5;

int n, a[N], cnt = 0;
int sz[N], son[N], fa[N], id[N], top[N], na[N], dep[N], p[N];
vector<int> G[N];

class SegmentTree
{
private:
	struct Node
	{
		int l, r, maxn;
	}tree[N << 2];
	void push_up(int u)
	{
		tree[u].maxn = max(tree[u << 1].maxn, tree[u << 1 | 1].maxn);
	}
public:
	void build(int u, int l, int r)
	{
		tree[u] = { l, r, 0 };
		if (l == r) tree[u].maxn = na[r];
		else
		{
			int mid = (l + r) >> 1;
			build(u << 1, l, mid);
			build(u << 1 | 1, mid + 1, r);
			push_up(u);
		}
	}
	void update(int u, int x, int v)
	{
		if (tree[u].l == x && tree[u].r == x)
		{
			tree[u].maxn = v;
		}
		else
		{
			int mid = (tree[u].l + tree[u].r) >> 1;
			if (x <= mid) update(u << 1, x, v);
			else update(u << 1 | 1, x, v);
			push_up(u);
		}
	}
	int query(int u, int l, int r)
	{
		if (tree[u].l >= l && tree[u].r <= r) return tree[u].maxn;
		int mid = (tree[u].l + tree[u].r) >> 1, s = 0;
		if (l <= mid) s = query(u << 1, l, r);
		if (r > mid) s = max(s, query(u << 1 | 1, l, r));
		return s;
	}
};

class TreeCut
{
private:
	void dfs1(int u, int father, int depth)
	{
		dep[u] = depth;
		fa[u] = father;
		sz[u] = 1;
		for (int i = 0; i < G[u].size(); i++)
		{
			int nx = G[u][i];
			if (nx == father) continue;
			dfs1(nx, u, depth + 1);
			sz[u] += sz[nx];
			if (sz[son[u]] < sz[nx]) son[u] = nx;
		}
	}
	void dfs2(int u, int tf)
	{
		top[u] = tf;
		++cnt;
		id[u] = cnt;
		na[cnt] = a[u];
		if (!son[u]) return;
		dfs2(son[u], tf);
		for (int i = 0; i < G[u].size(); i++)
		{
			int nx = G[u][i];
			if (nx == fa[u] || nx == son[u]) continue;
			dfs2(nx, nx);
		}
	}
public:
	SegmentTree tree;
	void build()
	{
		dfs1(1, 1, 1);
		dfs2(1, 1);
		tree.build(1, 1, n);
	}
	void update(int k, int g)
	{
		int place = p[k];
		tree.update(1, id[place], g);
	}
	int query(int u, int v)
	{
		if (u == v) return 0;
		int res = 0;
		while (top[u] ^ top[v])
		{
			if (dep[top[u]] < dep[top[v]]) swap(u, v);
			res = max(res, tree.query(1, id[top[u]], id[u]));
			u = fa[top[u]];
		}
		if (dep[u] < dep[v]) swap(u, v);
		res = max(res, tree.query(1, dep[v] + 1, dep[u]));
		return res;
	}
};

TreeCut tc;

int main()
{
	scanf("%d", &n);
	for (int i = 1; i < n; i++)
	{
		int u, v, w;
		scanf("%d %d %d", &u, &v, &w);
		G[u].push_back(v);
		G[v].push_back(u);
		a[v] = w;
		p[i] = v;
	}
	tc.build();
	string s;
	while (cin >> s)
	{
		if (s == "DONE") break;
		int u, v;
		scanf("%d %d", &u, &v);
		if (s == "CHANGE") tc.update(u, v);
		else printf("%d\n", tc.query(u, v));
	}
	return 0;
}