#include <bits/stdc++.h>

std::vector<int> *adjacent_vertexes;
char *s;
int n, *max_length, *cnt;
long long ans;

void pre_dfs(int u, int parent) {
	max_length[u] = 0;
	cnt[u] = (s[u] == '1');
	for (int v: adjacent_vertexes[u]) {
		if(v != parent) {
			pre_dfs(v, u);
			max_length[u] = std::max(max_length[v] + 1, max_length[u]);
			cnt[u] += cnt[v];
		}
	}
	return;
}

void dfs(int u, int parent, int max_length_from_parent) {
	int first_max = 0, second_max = 0, first_max_rem;
	if(~parent) {
		first_max = max_length_from_parent;
		first_max_rem = parent;
	}
	for (int v: adjacent_vertexes[u]) {
		if(v != parent) {
			int tmp = max_length[v] + 1;
			if(tmp > first_max) {
				second_max = first_max;
				first_max = tmp;
				first_max_rem = v;
			}
			else if(tmp > second_max) {
				second_max = tmp;
			}
		}
	}
	int low_bound = n + 1;
	if(cnt[u] != cnt[0]) {
		low_bound = max_length_from_parent;
	}
	for (int v: adjacent_vertexes[u]) {
		if(v != parent) {
			int max_length_from_u = v == first_max_rem ? second_max : first_max, ok = 0;
			if(max_length_from_u >= max_length[v]) {
				if(cnt[v]) {
					ok = 1;
				}
			}
			if(max_length_from_u <= max_length[v]) {
				if(cnt[v] != cnt[0]) {
					ok = 1;
				}
			}
			ans += ok;
			dfs(v, u, max_length_from_u + 1);
			if(cnt[v]) {
				low_bound = std::min(low_bound, max_length[v] + 1);
			}
		}
	}
	if(s[u] == '1') {
		ans += second_max + 1;
	}
	else {
		if(low_bound <= second_max) {
			ans += second_max - low_bound + 1;
		}
	}
	return;
}

int main() {
	scanf("%d", &n);
	adjacent_vertexes = new std::vector<int>[n];
	max_length = new int[n];
	s = new char[n];
	cnt = new int[n];
	for (int i = 1; i < n; ++i) {
		int u, v;
		scanf("%d%d", &u, &v);
		adjacent_vertexes[--u].push_back(--v);
		adjacent_vertexes[v].push_back(u);
	}
	scanf("%s", s);
	pre_dfs(0, -1);
	dfs(0, -1, 0);
	printf("%lld\n", ans);
	return 0;
}