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

typedef long long ll;
const int MAXN = 1e5 + 5;
#define ls(x) (x << 1)
#define rs(x) (x << 1 | 1)
const ll NONE = 1e18;

char ch[20];
int n, u, v, head[MAXN], EdgeCnt;
ll ww;

struct Edge {
	int v, pre;
	ll ww;
} e[MAXN << 1];

void AddEdge(int u, int v, ll ww) {
	EdgeCnt ++;
	e[EdgeCnt].v = v;
	e[EdgeCnt].ww = ww;
	e[EdgeCnt].pre = head[u];
	head[u] = EdgeCnt;
}

ll w[MAXN];
int cnt, fa[MAXN], dep[MAXN], siz[MAXN], son[MAXN], dfn[MAXN], top[MAXN], rnk[MAXN];

void dfs1(int x) {
	son[x] = -1;
	siz[x] = 1;
	for(int i = head[x]; i; i = e[i].pre) {
		int to = e[i].v;
		if(!dep[to]) {
			dep[to] = dep[x] + 1;
			fa[to] = x;
			w[to] = e[i].ww;
			dfs1(to);
			siz[x] += siz[to];
			if(son[x] == -1 || siz[to] > siz[son[x]]) son[x] = to;
		}
	}
}

void dfs2(int x, int t) {
	top[x] = t;
	++cnt;
	dfn[x] = cnt;
	rnk[cnt] = x;
	if(son[x] == -1) return;
	dfs2(son[x], t);
	for(int i = head[x]; i; i = e[i].pre) {
		int to = e[i].v;
		if(to != fa[x] && to != son[x])
			dfs2(to, to);
	}
}

struct SegmentTree {
	ll maxn[MAXN << 3], tag1[MAXN << 3], tag2[MAXN << 3];
	
	void push_up(int p) {
		maxn[p] = max(maxn[ls(p)], maxn[rs(p)]);
	}
	
	void build(int p, int l, int r) {
		tag1[p] = 0; tag2[p] = NONE;
		if(l == r) {
			maxn[p] = w[rnk[l]];
			return;
		}
		int mid = (l + r) >> 1;
		build(ls(p), l, mid);
		build(rs(p), mid + 1, r);
		push_up(p);
	}
	
	void push_down(int p, int l, int r) {
		if(tag2[p] != NONE) {
			maxn[ls(p)] = tag2[p];
			maxn[rs(p)] = tag2[p];
			tag1[ls(p)] = 0;
			tag1[rs(p)] = 0;
			tag2[ls(p)] = tag2[p];
			tag2[rs(p)] = tag2[p];
			tag2[p] = NONE;
		}
		if(tag1[p]) {
			maxn[ls(p)] += tag1[p];
			maxn[rs(p)] += tag1[p];
			tag1[ls(p)] += tag1[p];
			tag1[rs(p)] += tag1[p];
			tag1[p] = 0;
		}
	}
	
	void add(int p, int nl, int nr, int l, int r, ll v) {
		if(nl <= l && r <= nr) {
			if(tag2[p] != NONE) {
				maxn[ls(p)] = tag2[p];
				maxn[rs(p)] = tag2[p];
				tag2[ls(p)] = tag2[p];
				tag2[rs(p)] = tag2[p];
				tag1[ls(p)] = 0;
				tag2[rs(p)] = 0;
				tag2[p] = NONE;
			}
			maxn[p] += v;
			tag1[p] += v;
			return;
		}
		push_down(p, l, r);
		int mid = (l + r) >> 1;
		if(nl <= mid) add(ls(p), nl, nr, l, mid, v);
		if(mid < nr) add(rs(p), nl, nr, mid + 1, r, v);
		push_up(p);
	}
	
	void cover_X(int p, int l, int r, int x, ll v) {
		if(l == r) {
			maxn[p] = v;
			tag1[p] = 0;
			tag2[p] = v;
			return;
		}
		push_down(p, l, r);
		int mid = (l + r) >> 1;
		if(x <= mid) cover_X(ls(p), l, mid, x, v);
		else cover_X(rs(p), mid + 1, r, x, v);
		push_up(p);
	}
	
	void cover(int p, int nl, int nr, int l, int r, ll v) {
		if(nl <= l && r <= nr) {
			maxn[p] = v;
			tag1[p] = 0;
			tag2[p] = v;
			return;
		}
		push_down(p, l, r);
		int mid = (l + r) >> 1;
		if(nl <= mid) cover(ls(p), nl, nr, l, mid, v);
		if(mid < nr) cover(rs(p), nl, nr, mid + 1, r, v);
		push_up(p);
	}
	
	ll query(int p, int nl, int nr, int l, int r) {
		if(nl <= l && r <= nr) return maxn[p];
		push_down(p, l, r);
		int mid = (l + r) >> 1; ll ret = LONG_LONG_MIN;
		if(nl <= mid) ret = max(ret, query(ls(p), nl, nr, l, mid));
		if(mid < nr) ret = max(ret, query(rs(p), nl, nr, mid + 1, r));
		return ret;
	}
} st;

void Cover(int x, int y, ll ww) {
	int fx = top[x], fy = top[y];
	while(fx != fy) {
		if(dep[fx] >= dep[fy])
			st.cover(1, dfn[fx], dfn[x], 1, n, ww), x = fa[fx];
		else
			st.cover(1, dfn[fy], dfn[y], 1, n, ww), y = fa[fy];
		fx = top[x];
		fy = top[y];
	}
	if(dfn[x] < dfn[y]) st.cover(1, dfn[x] + 1, dfn[y], 1, n, ww);
	else st.cover(1, dfn[y] + 1, dfn[x], 1, n, ww);
}

void Add(int x, int y, ll ww) {
	int fx = top[x], fy = top[y];
	while(fx != fy) {
		if(dep[fx] >= dep[fy])
			st.add(1, dfn[fx], dfn[x], 1, n, ww), x = fa[fx];
		else
			st.add(1, dfn[fy], dfn[y], 1, n, ww), y = fa[fy];
		fx = top[x];
		fy = top[y];
	}
	if(dfn[x] < dfn[y]) st.add(1, dfn[x] + 1, dfn[y], 1, n, ww);
	else st.add(1, dfn[y] + 1, dfn[x], 1, n, ww);
}

ll Max(int x, int y) {
	int fx = top[x], fy = top[y];
	ll ret = LONG_LONG_MIN;
	while(fx != fy) {
		if(dep[fx] >= dep[fy])
			ret = max(ret, st.query(1, dfn[fx], dfn[x], 1, n)), x = fa[fx];
		else
			ret = max(ret, st.query(1, dfn[fy], dfn[y], 1, n)), y = fa[fy];
		fx = top[x];
		fy = top[y];
	}
	if(dfn[x] < dfn[y]) ret = max(ret, st.query(1, dfn[x] + 1, dfn[y], 1, n));
	else ret = max(ret, st.query(1, dfn[y] + 1, dfn[x], 1, n));
	return ret;
}

int main() {
	scanf("%d", &n);
	for(int i = 1; i < n; ++i) {
		scanf("%d%d%lld", &u, &v, &ww);
		AddEdge(u, v, ww); AddEdge(v, u, ww);
	}
	dep[1] = 1;
	dfs1(1); dfs2(1, 1);
	st.build(1, 1, n);
	while(1) {
		scanf("%s", ch);
		while(!strcmp(ch, "")) scanf("%s", ch);
		if(ch[0] == 'S') break;
		if(ch[0] == 'C' && ch[1] == 'h') {
			scanf("%d%lld", &u, &ww);
			int a = e[2 * u - 1].v, b = e[2 * u].v;
			if(fa[a] == b)
				st.cover_X(1, 1, n, dfn[a], ww);
			else
				st.cover_X(1, 1, n, dfn[b], ww);
		}
		else if(ch[0] == 'C') {
			scanf("%d%d%lld", &u, &v, &ww);
			Cover(u, v, ww);
		}
		else if(ch[0] == 'A') {
			scanf("%d%d%lld", &u, &v, &ww);
			Add(u, v, ww);
		}
		else {
			scanf("%d%d", &u, &v);
			printf("%lld\n", Max(u, v));
		}
	}
	return 0;
}

一直找不出问题在哪，样例也都对，但提交后就是全 WA