#include<bits/stdc++.h>
using namespace std;
const int MX = 200005;
vector<int>g[MX];
int n;
int dp[MX];
string s;
int ans;
int solve(int v, int p=-1) {
int &ret = dp[v];
ret = 0;
if(s[v]=='0') {
for(auto u : g[v]) if(u!=p) {
ret += solve(u, v);
}
} else {
int mx = 0, sum = 0;
for(auto u : g[v]) if(u!=p) {
mx = max(mx, solve(u, v));
sum += solve(u, v);
}
mx += 1;
sum -= 1;
ans = max({mx, ans, sum});
ret = max(1, sum);
}
return ret;
}
void PlayGround() {
cin >> n;
for(int i=1; i<n; ++i) {
int u, v; cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
cin >> s;
s = "#" + s;
cout << max(ans, solve(1)) << endl;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
PlayGround();
return 0;
}
