#include <iostream>
#include <vector>
#include <cstring>
using namespace std;
const int nmax = 2e3 + 2;
vector<vector<int>> adj;
int sum[nmax], f[nmax], viz[nmax];
string s;
void dfs(int i, int cum_from, int add) {
if(add == 1) {
if(cum_from == 2) {
sum[i] = add;
}
}
if(cum_from == 1) {
cum_from ++;
}
for(auto it : adj[i]) {
if(!viz[it]) {
viz[it] = 1;
int curr_add = add;
if(s[it] == '1') {
curr_add = 1;
}
if(s[i] == '1' && cum_from == 0) {
dfs(it, cum_from + 1, curr_add);
} else {
dfs(it, cum_from, curr_add);
}
}
}
}
int main() {
int n;
cin >> n;
adj.resize(n + 1);
for(int i = 1; i < n; i ++) {
int a, b;
cin >> a >> b;
adj[a].push_back(b);
adj[b].push_back(a);
f[a] ++;
f[b] ++;
}
cin >> s;
s = '0' + s;
for(int i = 1; i <= n; i ++) {
memset(viz, 0, sizeof(viz));
viz[i] = 1;
if(s[i] == '0') {
dfs(i, 0, 0);
} else {
dfs(i, 0, 1);
}
}
int ans = 0;
for(int i = 1; i <= n; i ++) {
if(s[i] == '1') {
ans ++;
int cnt = 0;
for(auto it : adj[i]) {
if(sum[it]) {
cnt ++;
}
}
if(cnt > 1) {
ans --;
}
}
}
cout << ans;
return 0;
}
