#include <cstdio>

#include <iostream>

#define maxn 100010

int head[maxn], cnt;

struct Edge {

	int to, nxt;

} e[maxn << 1];

int ind[maxn];

inline void addedge(int a, int b) {

	e[++cnt] = (Edge) {b, head[a]}; head[a] = cnt;

	e[++cnt] = (Edge) {a, head[b]}; head[b] = cnt;

}

int w[maxn];

namespace SAM {

#define N (maxn * 22 << 1)

	int lst = 1, idx = 1;

	int R[N], fail[N], nxt[N][10];

	void append(int ch) {

		int p = lst, np = lst = ++idx; R[np] = R[p] + 1;

		for (; p && !nxt[p][ch]; p = fail[p]) nxt[p][ch] = np;

		if (!p) fail[np] = 1;

		else {

			int q = nxt[p][ch];

			if (R[p] + 1 == R[q]) fail[np] = q;

			else {

				int nq = ++idx;

				R[nq] = R[p] + 1, fail[nq] = fail[q], fail[q] = fail[np] = nq;

				std::copy(nxt[q], nxt[q] + 10, nxt[nq]);

				for (; nxt[p][ch] == q; p = fail[p]) nxt[p][ch] = nq;

			}

		}

	}

	void dfs(int u, int fa = 0) {

		append(w[u]);

		int tmp = lst;

		for (int i = head[u]; i; i = e[i].nxt) {

			int v = e[i].to;

			if (v != fa) dfs(v, u), lst = tmp;

		}

	}

	long long query() {

		long long ans = 0;

		for (int i = 2; i <= idx; i++) ans += R[i] - R[fail[i]];

		return ans;

	}

#undef N

}

int n, m;

int main() {

	scanf("%d%d", &n, &m);

	for (int i = 1; i <= n; i++) scanf("%d", w + i);

	for (int i = 1, a, b; i < n; i++) {

		scanf("%d%d", &a, &b);

		addedge(a, b); ind[a]++, ind[b]++;

	}

	for (int i = 1; i <= n; i++) if (ind[i] == 1) {

		SAM::lst = 1;

		SAM::dfs(i);

	}

	printf("%lld\n", SAM::query());

	return 0;

}