#include<iostream>

#include<cstdio>

#include<cstring>

#include<cctype>

using namespace std;

template <typename T> inline T min(T &a,T &b) {return a<b ?a:b;}

template <typename T> inline T max(T &a,T &b) {return a>b ?a:b;}

template <typename T> inline void read(T &x){

    char c=getchar(); x=; bool f=;

    while(!isdigit(c)) f= !f||c=='-' ? :,c=getchar();

    while(isdigit(c)) x=(x<<)+(x<<)+(c^),c=getchar();

    x= f ? x:-x;

}

template <typename T> inline void output(T x){

    if(!x) {putchar(); return ;}

    if(x<) putchar('-'),x=-x;

    int wt[],l=;

    while(x) wt[++l]=x%,x/=;

    while(l) putchar(wt[l--]+);

}

typedef int arr[];

int n,m,cnt,tot;

arr d,fa,siz,bgs,tp,tmp,val,id,hd,ed;

int nxt[],poi[];

int lx[],rx[],sum[],tag[];

inline void add_(int x,int y){

    nxt[ed[x]]=++cnt; hd[x]= hd[x] ? hd[x]:cnt;

    ed[x]=cnt; poi[cnt]=y;

}

inline void pushdown(int o){

    if(tag[o]==-) return ;

    int lc=o<<,rc=o<<|;

    sum[lc]=sum[rc]=;

    lx[lc]=rx[lc]=lx[rc]=rx[rc]=tag[o];

    tag[lc]=tag[rc]=tag[o];

    tag[o]=-;

}

inline void maintain(int o){

    int lc=o<<,rc=o<<|;

    lx[o]=lx[lc],rx[o]=rx[rc],sum[o]=sum[lc]+sum[rc];

    if(rx[lc]==lx[rc]) --sum[o]; //重复减掉

}

inline void build(int o,int l,int r){

    tag[o]=-;

    if(l==r) {tag[o]=lx[o]=rx[o]=tmp[l]; sum[o]=; return ;}

    int lc=o<<,rc=o<<|,mid=l+((r-l)>>);

    build(lc,l,mid); build(rc,mid+,r);

    maintain(o);

}

inline void modify(int o,int l,int r,int x1,int x2,int v){

    if(x1<=l&&r<=x2){

        lx[o]=rx[o]=tag[o]=v; sum[o]=;

        return ;

    }pushdown(o);

    int lc=o<<,rc=o<<|,mid=l+((r-l)>>);

    if(x1<=mid) modify(lc,l,mid,x1,x2,v);

    if(x2>mid) modify(rc,mid+,r,x1,x2,v);

    maintain(o);

}

inline int query(int o,int l,int r,int x1,int x2){

    if(x1<=l&&r<=x2) return sum[o];

    pushdown(o); int res=;

    int lc=o<<,rc=o<<|,mid=l+((r-l)>>);

    if(x1<=mid) res+=query(lc,l,mid,x1,x2);

    if(x2>mid){

        res+=query(rc,mid+,r,x1,x2);

        if(x1<=mid&&rx[lc]==lx[rc]) --res;

    }return res;

}

inline void dfs1(int x,int _fa){

    d[x]=d[_fa]+,fa[x]=_fa,siz[x]=;

    for(int i=hd[x];i;i=nxt[i])

        if(poi[i]!=_fa){

            dfs1(poi[i],x);

            siz[x]+=siz[poi[i]];

            if(siz[bgs[x]]<siz[poi[i]]) bgs[x]=poi[i];

        }

}

inline void dfs2(int x,int _top){

    id[x]=++tot,tmp[tot]=val[x],tp[x]=_top;

    if(siz[x]==) return;

    dfs2(bgs[x],_top);

    for(int i=hd[x];i;i=nxt[i])

        if(poi[i]!=fa[x]&&poi[i]!=bgs[x])

            dfs2(poi[i],poi[i]);

}

inline int findcol(int o,int l,int r,int x){

    if(l==r) return tag[o];

    pushdown(o);

    int lc=o<<,rc=o<<|,mid=l+((r-l)>>);

    if(x<=mid) return findcol(lc,l,mid,x);

    else return findcol(rc,mid+,r,x);

}

inline void change(int x,int y,int v){

    while(tp[x]!=tp[y]){ //™模板原来这里多套了个d数组上去，变成50pts

        if(d[tp[x]]<d[tp[y]]) swap(x,y);

        modify(,,n,id[tp[x]],id[x],v);

        x=fa[tp[x]];

    }if(d[x]>d[y]) swap(x,y);

    modify(,,n,id[x],id[y],v);

}

inline int ask(int x,int y){

    int res=,r1,r2;

    while(tp[x]!=tp[y]){

        if(d[tp[x]]<d[tp[y]]) swap(x,y);

        res+=query(,,n,id[tp[x]],id[x]);

        r1=findcol(,,n,id[tp[x]]);

        r2=findcol(,,n,id[fa[tp[x]]]);

        if(r1==r2) --res;

        x=fa[tp[x]];

    }if(d[x]>d[y]) swap(x,y);

    res+=query(,,n,id[x],id[y]);

    return max(res,);

}

int main(){

    read(n); read(m); int q1,q2,q3; char opt[];

    for(int i=;i<=n;++i) read(val[i]);

    for(int i=;i<n;++i) read(q1),read(q2),add_(q1,q2),add_(q2,q1);

    dfs1(,); dfs2(,); build(,,n);

    for(int i=;i<=m;++i){

        scanf("%s",opt); read(q1),read(q2);

        if(opt[]=='Q') output(ask(q1,q2)),putchar('\n');

        else read(q3),change(q1,q2,q3);

    }return ;

}