#include <bits/stdc++.h>
#define endl "\n"
using namespace std;
int N;
vector<int> graph[200000];
char s[200001];
int ans = 0;
int dfs(int id, int par){
int p = s[id] - '0', ret = p, c = 0, mxc = 0;
for(int i : graph[id]){
if(i == par) continue;
int cur = dfs(i, id);
if(cur == 0) continue;
c++;
mxc = max(mxc, cur);
ret += cur;
}
if(p && c > 0){
ans = (c-1 ? max({ans, ret-2, mxc+1}) : max(ans, ret));
ret -= 2;
}
ans = max(ans, ret);
return max(p, ret);
}
int32_t main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> N;
for(int i = 0; i < N-1; i++){
int a, b; cin >> a >> b;
graph[a-1].push_back(b-1);
graph[b-1].push_back(a-1);
}
cin >> s;
dfs(0, 0);
cout << ans << endl;
}
