#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<int, int> P;
template<typename T> inline void chkmin(T &a, const T &b) { a = a < b ? a : b; }
template<typename T> inline void chkmax(T &a, const T &b) { a = a > b ? a : b; }

const int MAXN = 200005;
vector<int> gra[MAXN];
int sz[MAXN], mx[MAXN], se[MAXN], mn[MAXN], n;
LL ans;
char str[MAXN];

void dfs1(int u, int fa) {
	sz[u] = str[u] == '1';
	mn[u] = str[u] == '1' ? 0 : 1e9;
	for (int v : gra[u]) if (v != fa) {
		dfs1(v, u);
		sz[u] += sz[v];
		int d = mx[v] + 1;
		if (d > mx[u]) se[u] = mx[u], mx[u] = d;
		else if (d > se[u]) se[u] = d;
		if (sz[v]) chkmin(mn[u], d);
	}
}

void dfs2(int u, int fa) {
	int mxd = min(mx[u] - 1, se[u] + 1);
	if (mxd >= mn[u]) ans += mxd - mn[u] + 1;
	for (int v : gra[u]) if (v != fa) {
		int d = mx[u] == mx[v] + 1 ? se[u] + 1 : mx[u] + 1;
		if (d > mx[v]) se[v] = mx[v], mx[v] = d;
		else if (d > se[v]) se[v] = d;
		if (sz[1] > sz[v]) chkmin(mn[v], d);
		dfs2(v, u);
	}
}

int main() {
	scanf("%d", &n);
	for (int i = 1; i < n; i++) {
		int u, v; scanf("%d%d", &u, &v);
		gra[u].push_back(v), gra[v].push_back(u);
	}
	scanf("%s", str + 1);
	dfs1(1, 0);
	dfs2(1, 0);
	printf("%lld\n", ans + 1);
	return 0;
}