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求指错

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<algorithm>
#define maxn 1001000
#define ls x<<1
#define rs x<<1|1

using namespace std;

int n,m;
int cnt,siz[maxn],tot,a[maxn],head[maxn];
int dfn[maxn],top[maxn],dep[maxn],fa[maxn],son[maxn],lazy[maxn],pre[maxn];

struct node{int l,r,tot;}col[maxn];
struct edge{int fr,to,nxt;}e[maxn];
void add(int fr,int to){e[++tot].fr=fr;e[tot].to=to;e[tot].nxt=head[fr];head[fr]=tot;}

int read() {
	int s=0,w=1;char ch=getchar();
	while(ch<'0'||ch>'9') {if(ch=='-') w=-1;ch=getchar();}
	while(ch>='0'&&ch<='9') s=(s<<1)+(s<<3)+ch-'0',ch=getchar();
	return s*w;
}

namespace Seg{
	void pushup(int x){
		col[x].l=col[ls].l;col[x].r=col[rs].r;
		col[x].tot=col[ls].tot+col[rs].tot;
		if(col[ls].r==col[rs].l) col[x].tot--;
	}
	
	void pushdown(int x){
		if(lazy[x]){
		    lazy[ls]=lazy[rs]=lazy[x];
		    col[ls].tot=col[rs].tot=1;
		    col[ls].l=col[ls].r=col[rs].r=col[rs].l=lazy[x];
		    lazy[x]=0;
		}
    }
	
	void build(int x,int l,int r){
		if(l==r){col[x].tot=1;col[x].l=col[x].r=a[pre[l]];return;}
		int mid=l+r>>1;
		build(ls,l,mid);build(rs,mid+1,r);
		pushup(x);
	}
	
	void Update(int x,int l,int r,int val,int L,int R){
		if(L<=l&&R>=r){col[x].l=col[x].r=lazy[x]=val;col[x].tot=1;return;}
		int mid=l+r>>1;
		pushdown(x);
		if(L<=mid) Update(ls,l,mid,val,L,R);
		if(R>=mid+1) Update(rs,mid+1,r,val,L,R);
		pushup(x);
	}
	
    int Getcol(int x,int l,int r,int rt){
		if(l==r) return col[x].l;
		int mid=l+r>>1;
		pushdown(x);
		if(rt<=mid) return Getcol(ls,l,mid,rt);
		else return Getcol(rs,mid+1,r,rt); 
	}
	
	int Query(int x,int l,int r,int L,int R){
		int ans=0;bool flag=0;
		if(L<=l&&R>=r) return col[x].tot;
		int mid=l+r>>1;
		pushdown(x);
		if(L<=mid){ans+=Query(ls,l,mid,l,R);flag=1;}
		if(R>=mid+1){ans+=Query(rs,mid+1,r,L,R);if(flag==1){if(col[ls].r==col[rs].l) ans--;}}
		return ans;
    }
}

namespace Cut{
	void dfs1(int x,int Fa){
		fa[x]=Fa;dep[x]=dep[Fa]+1;siz[x]=1;
		for(int i=head[x];i;i=e[i].nxt){
			int to=e[i].to;
			if(to==fa[x]) continue;
			dfs1(to,x);
			siz[x]+=siz[to];
			if(siz[son[x]]<siz[to]) son[x]=to;
		}
	}
	
	void dfs2(int x,int tp){
		top[x]=tp;dfn[x]=++cnt;pre[cnt]=x;
		if(son[x]) dfs2(son[x],tp);
		for(int i=head[x];i;i=e[i].nxt){
			int to=e[i].to;
			if(to==fa[x]||to==son[x]) continue;
			dfs2(to,to);
		}
	}
	
	void change(int x,int y,int val){
		while(top[x]!=top[y]){
			if(dep[top[x]]<dep[top[y]]) swap(x,y);
			Seg::Update(1,1,n,val,dfn[top[x]],dfn[x]);
			x=fa[top[x]];
		}
		if(dep[x]>dep[y]) swap(x,y);
		Seg::Update(1,1,n,val,dfn[x],dfn[y]);
	}
	
	int ask(int x,int y){
		int ans=0;
		while(top[x]!=top[y]){
			if(dep[top[x]]<dep[top[y]]) swap(x,y);
			ans+=Seg::Query(1,1,n,dfn[top[x]],dfn[x]);
			if(Seg::Getcol(1,1,n,dfn[top[x]])==Seg::Getcol(1,1,n,dfn[fa[top[x]]])) ans--;
			x=fa[top[x]];
		}
		if(dep[x]>dep[y]) swap(x,y);
		ans+=Seg::Query(1,1,n,dfn[x],dfn[y]);
		return ans;
	}
}

int main(){
	n=read();m=read();
	for(int i=1;i<=n;i++) a[i]=read();
	for(int i=1,u,v;i<n;i++){u=read();v=read();add(u,v);add(v,u);}
	
	Cut::dfs1(1,0);Cut::dfs2(1,1);Seg::build(1,1,n); 
	for(int i=1,as,bs,cs;i<=m;i++){
		char opt;cin>>opt;as=read();bs=read();
		if(opt=='C'){cs=read();Cut::change(as,bs,cs);}
		if(opt=='Q')printf("%d\n",Cut::ask(as,bs)); 
	}
	return 0;
}