//Author: Kevin
#include<bits/stdc++.h>
//#pragma GCC optimize("O2")
using namespace std;
#define ll long long
#define ull unsigned ll
#define pb emplace_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
#define inf 0x3f3f3f3f
#define pii pair<int,int>
#define lb(v,x) (int)(lower_bound(ALL(v),x)-v.begin())
#define ub(v,x) (int)(upper_bound(ALL(v),x)-v.begin())
#define uni(v) v.resize(unique(ALL(v))-v.begin())
#define longer __int128_t
void die(string S){puts(S.c_str());exit(0);}
const int maxn=2000005;
int n,c;
int trie[maxn][10],tot=1;
int nd[maxn];
int trans[maxn*2][10],fail[maxn*2],len[maxn*2],cnt=1;
int color[100100];
vector<int> G[100100];
void dfs(int u,int fa,int nd)
{
	if(!trie[nd][color[u]])
		trie[nd][color[u]]=++tot;
	nd=trie[nd][color[u]];
	for(auto v:G[u])
		if(v!=fa)
			dfs(v,u,nd);
}
int qu[maxn*2],hd,ta;
int extend(int p,int x)
{
	int np=++cnt;
	len[np]=len[p]+1;
	while(p&&!trans[p][x])
	{
		trans[p][x]=np;
		p=fail[p];
	}
	if(!p) fail[np]=1;
	else
	{
		int q=trans[p][x];
		if(len[p]+1==len[q])
			fail[np]=q;
		else
		{
			int nq=++cnt;
			len[nq]=len[p]+1;
			memcpy(trans[nq],trans[q],sizeof(int)*10);
			fail[nq]=fail[q];
			fail[q]=fail[np]=nq;
			while(p&&trans[p][x]==q)
			{
				trans[p][x]=nq;
				p=fail[p];
			}
		}
	}
	return np;
}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>n>>c;
	for(int i=1;i<=n;i++)
		cin>>color[i];
	for(int i=1;i<n;i++)
	{
		int u,v;
		cin>>u>>v;
		G[u].pb(v);
		G[v].pb(u);
	}
	for(int i=1;i<=n;i++)
		if(sz(G[i])==1)
			dfs(i,0,1);
	qu[ta++]=1;
	nd[1]=1;
	while(hd<=ta)
	{
		int x=qu[hd++];
		for(int i=0;i<c;i++)
			if(trie[x][i])
			{
				nd[trie[x][i]]=extend(nd[x],i);
				qu[ta++]=trie[x][i];
			}
	}
	ll ans=0;
	for(int i=1;i<=cnt;i++)
		ans+=len[i]-len[fail[i]];
	cout<<ans<<'\n';
	return 0;
}