#include <algorithm>
#include <cstdio>
#include <vector>
#define pb push_back
std::vector<int> adj[200005];
int sz[200005], mx[200005], sec[200005], low[200005];
char col[200005];
long long ans;
void dfs(int u, int fa = -1)
{
	sz[u] = col[u] - '0';
	low[u] = col[u] == '1' ? 0 : 1e9;
	for (int v : adj[u])
	{
		if (v == fa)
			continue;
		dfs(v, u);
		if (mx[v] + 1 > mx[u])
		{
			sec[u] = mx[u];
			mx[u] = mx[v] + 1;
		}
		else
			sec[u] = std::max(sec[u], mx[v] + 1);
		sz[u] += sz[v];
		if (sz[v])
			low[u] = std::min(low[u], mx[v] + 1);
	}
}
void work(int u, int fa = -1)
{
	if (u)
	{
		int x = mx[fa] == mx[u] + 1 ? sec[fa] : mx[fa];
		if (x + 1 > mx[u])
		{
			sec[u] = mx[u];
			mx[u] = x + 1;
		}
		else
			sec[u] = std::max(sec[u], x + 1);
		if (sz[0] - sz[u])
			low[u] = std::min(low[u], x + 1);
	}
	ans += std::max(0, std::min(sec[u] + 1, mx[u] - 1) - low[u] + 1);
	for (int v : adj[u])
	{
		if (v != fa)
			work(v, u);
	}
}
int main()
{
	// freopen("AGC008-F.in", "r", stdin);
	int n;
	scanf("%d", &n);
	for (int i = 1; i < n; i++)
	{
		int u, v;
		scanf("%d%d", &u, &v);
		adj[--u].pb(--v);
		adj[v].pb(u);
	}
	scanf("%s", col);
	dfs(0);
	work(0);
	printf("%lld\n", ans + 1);
	return 0;
}
