#include <cstdio>

#include <iostream>

#include <algorithm>

#define maxn 200001

using namespace std;

struct TreeNodeType {

    int l,r,dis,lc,rc,flag,mid;

};

struct TreeNodeType tree[maxn<<];

struct EdgeType {

    int to,next;

};

struct EdgeType edge[maxn<<];

int n,m,if_z,dis[maxn],flag[maxn],dis_[maxn];

int size[maxn],head[maxn],deep[maxn],f[maxn];

int cnt,tot,num,belong[maxn];

char Cget;

inline void read_int(int &now)

{

    now=,if_z=,Cget=getchar();

    while(Cget>''||Cget<'')

    {

        if(Cget=='-') if_z=-;

        Cget=getchar();

    }

    while(Cget>=''&&Cget<='')

    {

        now=now*+Cget-'';

        Cget=getchar();

    }

    now*=if_z;

}

inline void edge_add(int from,int to)

{

    edge[++num].to=from,edge[num].next=head[to],head[to]=num;

    edge[++num].to=to,edge[num].next=head[from],head[from]=num;

}

void search(int now,int fa)

{

    int pos=cnt++;

    deep[now]=deep[fa]+,f[now]=fa;

    for(int i=head[now];i;i=edge[i].next)

    {

        if(edge[i].to==fa) continue;

        search(edge[i].to,now);

    }

    size[now]=cnt-pos;

}

void search_(int now,int chain)

{

    belong[now]=chain,flag[now]=++cnt;

    dis_[flag[now]]=dis[now];

    int pos=;

    for(int i=head[now];i;i=edge[i].next)

    {

        if(edge[i].to==f[now]) continue;

        if(size[edge[i].to]>size[pos]) pos=edge[i].to;

    }

    if(pos!=) search_(pos,chain);

    else return ;

    for(int i=head[now];i;i=edge[i].next)

    {

        if(edge[i].to==f[now]||edge[i].to==pos) continue;

        search_(edge[i].to,edge[i].to);

    }

}

inline void tree_up(int now)

{

    if(tree[now<<].rc==tree[now<<|].lc)

    {

        tree[now].dis=tree[now<<].dis+tree[now<<|].dis-;

    }

    else

    {

        tree[now].dis=tree[now<<].dis+tree[now<<|].dis;

    }

    tree[now].lc=tree[now<<].lc,tree[now].rc=tree[now<<|].rc;

}

inline void tree_down(int now)

{

    if(tree[now].l==tree[now].r) return ;

    tree[now<<].dis=,tree[now<<|].dis=;

    tree[now<<].lc=tree[now<<].rc=tree[now].flag;

    tree[now<<|].lc=tree[now<<|].rc=tree[now].flag;

    tree[now<<].flag=tree[now<<|].flag=tree[now].flag;

    tree[now].flag=;

}

void tree_build(int now,int l,int r)

{

    tree[now].l=l,tree[now].r=r;

    if(l==r)

    {

        tree[now].lc=dis_[++cnt];

        tree[now].rc=tree[now].lc;

        tree[now].dis=;

        return ;

    }

    tree[now].mid=(l+r)>>;

    tree_build(now<<,l,tree[now].mid);

    tree_build(now<<|,tree[now].mid+,r);

    tree_up(now);

}

void tree_change(int now,int l,int r,int x)

{

    if(tree[now].l==l&&tree[now].r==r)

    {

        tree[now].dis=,tree[now].flag=x;

        tree[now].lc=tree[now].rc=x;

        return ;

    }

    if(tree[now].flag) tree_down(now);

    if(l>tree[now].mid) tree_change(now<<|,l,r,x);

    else if(r<=tree[now].mid) tree_change(now<<,l,r,x);

    else

    {

        tree_change(now<<,l,tree[now].mid,x);

        tree_change(now<<|,tree[now].mid+,r,x);

    }

    tree_up(now);

}

int tree_query(int now,int l,int r)

{

    if(tree[now].l==l&&tree[now].r==r)

    {

        return tree[now].dis;

    }

    if(tree[now].flag) tree_down(now);

    tree_up(now);

    if(l>tree[now].mid) return tree_query(now<<|,l,r);

    else if(r<=tree[now].mid) return tree_query(now<<,l,r);

    else

    {

        int ld=tree_query(now<<,l,tree[now].mid);

        int rd=tree_query(now<<|,tree[now].mid+,r);

        if(tree[now<<].rc==tree[now<<|].lc) return ld+rd-;

        else return ld+rd;

    }

}

int tree_query_color(int now,int to)

{

    if(tree[now].l==tree[now].r&&tree[now].l==to)

    {

        return tree[now].lc;

    }

    if(tree[now].flag) tree_down(now);

    tree_up(now);

    if(to>tree[now].mid) return tree_query_color(now<<|,to);

    else return tree_query_color(now<<,to);

}

inline void solve_change(int x,int y,int z)

{

    while(belong[x]!=belong[y])

    {

        if(deep[belong[x]]<deep[belong[y]]) swap(x,y);

        tree_change(,flag[belong[x]],flag[x],z);

        x=f[belong[x]];

    }

    tree_change(,min(flag[x],flag[y]),max(flag[x],flag[y]),z);

}

inline int solve_query(int x,int y)

{

    int ans=;

    while(belong[x]!=belong[y])

    {

        if(deep[belong[x]]<deep[belong[y]]) swap(x,y);

        ans+=tree_query(,flag[belong[x]],flag[x]);

        if(tree_query_color(,flag[belong[x]])==tree_query_color(,flag[f[belong[x]]])) ans--;

        x=f[belong[x]];

    }

    ans+=tree_query(,min(flag[x],flag[y]),max(flag[x],flag[y]));

    return ans;

}

int main()

{

    read_int(n),read_int(m);

    for(int i=;i<=n;i++) read_int(dis[i]);

    int from,to,pos;

    for(int i=;i<n;i++)

    {

        read_int(from),read_int(to);

        edge_add(from,to);

    }

    search(,),cnt=,search_(,),cnt=,tree_build(,,n);

    char type;

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

    {

        cin>>type;

        if(type=='C')

        {

            read_int(from),read_int(to),read_int(pos);

            solve_change(from,to,pos);

        }

        else

        {

            read_int(from),read_int(to);

            printf("%d\n",solve_query(from,to));

        }

    }

    return ;

}