CODE

#include <vector>
#include <queue>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long LL;
#define ls (i<<1)
#define rs (i<<1|1)
inline void read(int &num) {
	char ch; int flg=1; while(!isdigit(ch=getchar()))if(ch=='-')flg=-flg;
	for(num=0; isdigit(ch); num=num*10+ch-'0',ch=getchar()); num*=flg;
}
const int MAXN = 100005;

int n, q, w[MAXN], dfn[MAXN], seq[MAXN], tmr;
int fir[MAXN], cnt;
struct edge { int to, nxt; }e[MAXN<<1];

inline void add(int u, int v) {
	e[cnt] = (edge){ v, fir[u] }, fir[u] = cnt++;
	e[cnt] = (edge){ u, fir[v] }, fir[v] = cnt++;
}
int dep[MAXN], fa[MAXN], sz[MAXN], top[MAXN], son[MAXN];
void dfs(int u, int ff) {
	dep[u] = dep[fa[u]=ff] + (sz[u]=1);
	for(int v, i = fir[u]; ~i; i = e[i].nxt) 
		if((v=e[i].to) != fa[u]) {
			dfs(v, u), sz[u] += sz[v];
			if(sz[v] > sz[son[u]]) son[u] = v;
		}
}
void dfs2(int u, int tp) {
	top[u] = tp; seq[dfn[u] = ++tmr] = u;
	if(son[u]) dfs2(son[u], tp);
	for(int v, i = fir[u]; ~i; i = e[i].nxt)
		if((v=e[i].to) != son[u] && v != fa[u]) dfs2(v, v);
}
struct node {
	int lc, rc, sum;
	node(){ sum = -1; }
	node(int l, int r, int s):lc(l), rc(r), sum(s){}
	inline node operator +(const node &o)const {
		if(sum == -1) return o;
		if(o.sum == -1) return *this;
		if(rc == o.lc) return node(lc, o.rc, sum+o.sum-1);
		else return node(lc, o.rc, sum+o.sum);
	}
	inline friend node rev(const node &o) { return node(o.rc, o.lc, o.sum); }
}col[MAXN<<2];
int tag[MAXN<<2];
inline void upd(int i) {
	col[i] = col[ls] + col[rs];
}
inline void mt(int i) {
	if(~tag[i]) {
		col[ls] = col[rs] = node(tag[i], tag[i], 1);
		tag[ls] = tag[rs] = tag[i]; //忘了写这个WA到自闭
		tag[i] = -1;
	}
}
void build(int i, int l, int r) {
	tag[i] = -1;
	if(l == r) {
		col[i] = node(w[seq[l]], w[seq[l]], 1);
		return;
	}
	int mid = (l + r) >> 1;
	build(ls, l, mid);
	build(rs, mid+1, r);
	upd(i);
}
void cover(int i, int l, int r, int x, int y, int val) {
	if(l == x && r == y) {
		col[i] = node(val, val, 1);
		tag[i] = val;
		return;
	}
	int mid = (l + r) >> 1;
	mt(i);
	if(y <= mid) cover(ls, l, mid, x, y, val);
	else if(x > mid) cover(rs, mid+1, r, x, y, val);
	else cover(ls, l, mid, x, mid, val), cover(rs, mid+1, r, mid+1, y, val);
	upd(i);
}
node query(int i, int l, int r, int x, int y) {
	if(l == x && r == y) return col[i];
	int mid = (l + r) >> 1; node res;
	mt(i);
	if(y <= mid) res = query(ls, l, mid, x, y);
	else if(x > mid) res = query(rs, mid+1, r, x, y);
	else res = query(ls, l, mid, x, mid) + query(rs, mid+1, r, mid+1, y);
	upd(i);
	return res;
}
inline node Query(int x, int y) {
	node resx, resy;
	while(top[x] != top[y]) {
		if(dep[top[x]] > dep[top[y]]) resx = resx + rev(query(1, 1, n, dfn[top[x]], dfn[x])), x = fa[top[x]];
		else resy = query(1, 1, n, dfn[top[y]], dfn[y]) + resy, y = fa[top[y]];
	}
	if(dfn[x] < dfn[y]) return resx + query(1, 1, n, dfn[x], dfn[y]) + resy;
	else return resx + rev(query(1, 1, n, dfn[y], dfn[x])) + resy;
}
inline void Cover(int x, int y, int val) {
	while(top[x] != top[y]) {
		if(dep[top[x]] < dep[top[y]]) swap(x, y);
		cover(1, 1, n, dfn[top[x]], dfn[x], val);
		x = fa[top[x]];
	}
	if(dfn[x] < dfn[y]) swap(x, y);
	cover(1, 1, n, dfn[y], dfn[x], val);
}
int main() {
	read(n); read(q);
	for(int i = 1; i <= n; ++i) fir[i] = -1, read(w[i]);
	for(int i = 1, x, y; i < n; ++i)
		read(x), read(y), add(x, y);
	dfs(1, 0); dfs2(1, 1);
	build(1, 1, n);
	char s[2]; int x, y, z;
	while(q--) {
		while(!isalpha(s[0]=getchar()));
		read(x), read(y);
		if(s[0] == 'Q') printf("%d
", Query(x, y).sum);
		else read(z), Cover(x, y, z);
	}
}