#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <queue>
#include <vector>
#include <bitset>
#include <string>
#include <cmath>
#include <set>
#include <map>
#define Rep(i, x, y) for (int i = x; i <= y; i ++)
#define Dwn(i, x, y) for (int i = x; i >= y; i --)
#define RepE(i, x) for (int i = pos[x]; i; i = g[i].nex)
#define ev g[i].y
using namespace std;
typedef long long ll;
typedef double db;
const int N = 200005;
int n, sz, pos[N], m1[N], m2[N], low[N], b[N];
ll ans;
char s[N];
struct edge { int y, nex; } g[N * 2];
void init(int x, int y) { g[++ sz] = (edge) { y, pos[x] }, pos[x] = sz; }
void dfs1(int x, int fa) {
	low[x] = n;
	if (s[x] == '1') b[x] ++, low[x] = 0;
	RepE(i, x) if (ev != fa) {
		dfs1(ev, x);
		b[x] += b[ev];
		int z = m1[ev] + 1;
		if (m1[x] < z) m2[x] = m1[x], m1[x] = z;
		else m2[x] = max(m2[x], z);
		if (b[ev]) low[x] = min(low[x], z);
	}
}
void dfs2(int x, int fa) {
	RepE(i, x) if (ev != fa) {
		int z;
		if (m1[x] == m1[ev] + 1) z = m2[x] + 1;
		else z = m1[x] + 1;
		if (m1[ev] < z) m2[ev] = m1[ev], m1[ev] = z;
		else m2[ev] = max(m2[ev], z);
		if (b[ev] < b[1]) low[ev] = min(low[ev], z);
		dfs2(ev, x);
	}
//	cout <<x<<" "<< m1[x]<<" "<<m2[x]<<" "<<low[x]<<endl;
	int z = min(m2[x] + 1, m1[x] - 1);
	if (z >= low[x]) ans += z - low[x] + 1;
//	if (m1[x] == m2[x]) ans --;
}
int main()
{
	scanf ("%d", &n);
	Rep(i, 1, n - 1) {
		int x, y;
		scanf ("%d%d", &x, &y);
		init(x, y), init(y, x);
	}
	scanf ("%s", s + 1);
	dfs1(1, 0);
	dfs2(1, 0);
	printf("%lld\n", ans + 1);

	return 0;
}