#include <bits/stdc++.h>
#define endl "\n"
using namespace std;
int N;
vector<int> graph[200000];
char s[200000];
bool vis[200000];
int ans = 0;
int dfs(int id){
if(vis[id]) return 0;
vis[id] = true;
int p = s[id] - '0';
int ret = p;
int c = 0;
int mxc = 0;
for(int i : graph[id]){
int cur = dfs(i);
if(cur == 0) continue;
c++;
mxc = max(mxc, cur);
ret += cur;
}
if(p && c > 0){
if(c == 1){
ans = max(ans, ret);
(--ret)--;
}else{
(--ret)--;
ans = max({ans, ret, mxc+1});
}
}
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);
cout << ans << endl;
}
