#include <bits/stdc++.h>

typedef long long ll;
const int N = 200054, M = N * 2;

int n, E = 0;
int to[M], first[N], next[M];
int p[N], size[N];
int f[N], g[N], inf[N];
char s[N];
ll ans = 1;

inline void up(int &x, const int y) {x < y ? x = y : 0;}
inline void down(int &x, const int y) {x > y ? x = y : 0;}
inline int min(const int x, const int y) {return x < y ? x : y;}

inline void addedge(int u, int v) {
	to[++E] = v, next[E] = first[u], first[u] = E;
	to[++E] = u, next[E] = first[v], first[v] = E;
}

void dfs(int x) {
	int i, y; size[x] = s[x] &= 1;
	inf[x] = (s[x] - 1) & INT_MAX;
	for (i = first[x]; i; i = next[i])
		if ((y = to[i]) != p[x]) {
			p[y] = x, dfs(y), size[x] += size[y];
			f[x] <= f[y] ? (g[x] = f[x], f[x] = f[y] + 1) : (up(g[x], f[y] + 1), 0);
			if (size[y]) down(inf[x], f[y] + 1);
		}
}

void dfs2(int x, int fy = -1) {
	int i, y, sup;
	f[x] <= fy ? (g[x] = f[x], f[x] = fy + 1) : (up(g[x], fy + 1), 0);
	if (size[x] < size[1]) down(inf[x], fy + 1);
	if (inf[x] <= (sup = min(f[x] - 1, g[x] + 1))) ans += sup - inf[x] + 1;
	for (i = first[x]; i; i = next[i])
		if (p[y = to[i]] == x)
			dfs2(y, f[y] + 1 == f[x] ? g[x] : f[x]);
}

int main() {
	int i, u, v;
	scanf("%d", &n);
	for (i = 1; i < n; ++i) scanf("%d%d", &u, &v), addedge(u, v);
	scanf("%s", s + 1), dfs(1), dfs2(1);
	printf("%lld\n", ans);
	return 0;
}