#include<bits/stdc++.h>
using namespace std;
#define MAXN	200005
#define INF	1e9
template <typename T> void read(T &x) {
	x = 0; int f = 1;
	char c = getchar();
	for (; !isdigit(c); c = getchar()) if (c == '-') f = -f;
	for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';
	x *= f;
}
vector <int> a[MAXN];
int l[MAXN], r[MAXN], size[MAXN], n;
int mx[MAXN], home[MAXN], nx[MAXN];
char s[MAXN];
void updmin(int &x, int y) {
	x = min(x, y);
}
void updmax(int &x, int y) {
	x = max(x, y);
}
void update(int x, int y) {
	int value;
	if (home[y] == x) value = nx[y] + 1;
	else value = mx[y] + 1;
	if (value > mx[x]) {
		nx[x] = mx[x];
		mx[x] = value;
		home[x] = y;
	} else updmax(nx[x], value);
}
void dfs1(int pos, int fa) {
	size[pos] = s[pos] == '1';
	if (size[pos]) updmin(l[pos], 0);
	for (unsigned i = 0; i < a[pos].size(); i++)
		if (a[pos][i] != fa) {
			dfs1(a[pos][i], pos);
			update(pos, a[pos][i]);
			size[pos] += size[a[pos][i]];
			if (size[a[pos][i]]) updmin(l[pos], mx[a[pos][i]] + 1);
		}
}
void dfs2(int pos, int fa) {
	for (unsigned i = 0; i < a[pos].size(); i++)
		if (a[pos][i] != fa) {
			update(a[pos][i], pos);
			dfs2(a[pos][i], pos);
			if (size[1] - size[a[pos][i]]) {
				if (home[pos] == a[pos][i]) updmin(l[a[pos][i]], nx[pos] + 1);
				else updmin(l[a[pos][i]], mx[pos] + 1);
			}
		}
	r[pos] = min(mx[pos] - 1, nx[pos] + 1);
}
int main() {
	read(n);
	for (int i = 1; i < n; i++) {
		int x, y;
		read(x), read(y);
		a[x].push_back(y);
		a[y].push_back(x);
	}
	scanf("%s", s + 1);
	for (int i = 1; i <= n; i++)
		l[i] = INF;
	dfs1(1, 0);
	dfs2(1, 0);
	long long ans = 0;
	for (int i = 1; i <= n; i++)
		if (r[i] >= l[i]) ans += r[i] - l[i] + 1;
	cout << ans + 1 << endl;
	return 0;
}