#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
using namespace std;

typedef long long s64;

inline int getint()
{
	static char c;
	while ((c = getchar()) < '0' || c > '9');

	int res = c - '0';
	while ((c = getchar()) >= '0' && c <= '9')
		res = res * 10 + c - '0';
	return res;
}

const int MaxN = 200000;
const int INF = 0x3f3f3f3f;

int n;
char s[MaxN + 1];

vector<int> adj[MaxN + 1];

int dep[MaxN + 1][3];
int sum[MaxN + 1];

s64 res = 1ll;

int dfs1(const int &u, const int &fa)
{
	sum[u] = s[u] == '1';
	dep[u][0] = s[u] == '1' ? 0 : INF;

	for (int v : adj[u])
		if (v != fa)
		{
			sum[u] += dfs1(v, u);

			int d = dep[v][1] + 1;
			if (d > dep[u][1])
				dep[u][2] = dep[u][1], dep[u][1] = d;
			else if (d > dep[u][2])
				dep[u][2] = d;

			if (sum[v] > 0)
				dep[u][0] = min(dep[u][0], d);
		}

	return sum[u];
}

void dfs2(const int &u, const int &fa)
{
	for (int v : adj[u])
		if (v != fa)
		{
			int d = dep[u][dep[v][1] + 1 == dep[u][1] ? 2 : 1] + 1;
			if (d > dep[v][1])
				dep[v][2] = dep[v][1], dep[v][1] = d;
			else if (d > dep[v][2])
				dep[v][2] = d;

			if (sum[v] < sum[1])
				dep[v][0] = min(dep[v][0], d);

			dfs2(v, u);
		}

	int up = min(dep[u][1] - 1, dep[u][2] + 1);
	if (up >= dep[u][0])
		res += up - dep[u][0] + 1;
}

int main()
{
	cin >> n;
	for (int i = 1; i < n; ++i)
	{
		int u = getint(), v = getint();
		adj[u].push_back(v);
		adj[v].push_back(u);
	}

	scanf("%s", s + 1);

	dfs1(1, 0);
	dfs2(1, 0);

	cout << res << endl;

	return 0;
}