#include<bits/stdc++.h>
#define MAXN 4000010
#define FILE "read"
using namespace std;
typedef long long ll;
struct node{int y,next;}e[MAXN<<1];
int n,m,len,cnt(1),Link[MAXN],v[MAXN],d[MAXN],mx[MAXN],par[MAXN],tr[MAXN][15];
ll ans;
inline int read(){
	int x=0,f=1;  char ch=getchar();
	while(!isdigit(ch))  {if(ch=='-')  f=-1;  ch=getchar();}
	while(isdigit(ch))  {x=x*10+ch-'0';  ch=getchar();}
	return x*f;
}
void insert(int x,int y){e[++len].next=Link[x];Link[x]=len;e[len].y=y;d[y]++;}
int extend(int p,int x){
	int np=++cnt; mx[np]=mx[p]+1;
	while(p&&!tr[p][x])  tr[p][x]=np,p=par[p];
	if(!p)  par[np]=1;
	else{
		int q=tr[p][x];
		if(mx[q]==mx[p]+1) par[np]=q;
		else{
			int nq=++cnt; mx[nq]=mx[p]+1;
			memcpy(tr[nq],tr[q],sizeof(tr[q]));
			par[nq]=par[q];  par[q]=par[np]=nq;
			while(tr[p][x]==q&&p)  tr[p][x]=nq,p=par[p];
		}
	}
	return np;
}
void dfs(int x,int fa,int last){
	int now=extend(last,v[x]);
	for(int i=Link[x];i;i=e[i].next)
		if(e[i].y!=fa) dfs(e[i].y,x,now);
}
int main(){
	freopen(FILE".in","r",stdin);
	freopen(FILE".out","w",stdout);
	n=read();  m=read();
	for(int i=1;i<=n;++i)  v[i]=read();
	for(int i=1;i<n;++i){
		int x=read(),y=read();
		insert(x,y); insert(y,x);
	}
	for(int i=1;i<=n;++i)if(d[i]==1)dfs(i,0,1);
	for(int i=1;i<=cnt;++i) ans+=mx[i]-mx[par[i]];
	printf("%lld\n",ans);
	return 0;
}