#include<bits/stdc++.h>
#define st first
#define nd second
#define eb emplace_back
#define pb push_back
#define pp pop_back
#define all(x) x.begin(), x.end()
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
void debug(){cerr<<"\n";}
template<typename H, typename... T>
void debug(H h, T... t){cerr<<h;if(sizeof...(t))cerr<<", ";debug(t...);};
#define deb(x...) cerr<<#x<<" = ";debug(x);
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
const int N=2e5+5, INF=1e9+5;
vi E[N];
string s;
int dp[N];
int ans=0;
void dfs(int v, int p){
int m=0;
for(int u:E[v]){
if(u!=p){
dfs(u, v);
dp[v]+=dp[u];
m=max(m, dp[u]);
}
}
if(s[v-1]-'0'){
ans=max(ans, m+1);
dp[v]=max(1, dp[v]-1);
}
ans=max(ans, dp[v]);
//deb(v, dp[v]);
}
int main(){
//ios_base::sync_with_stdio(0);cin.tie(0);
int n;
cin>>n;
for(int i=1; i<n; i++){
int u, v;
cin>>u>>v;
E[u].pb(v);
E[v].pb(u);
}
cin>>s;
dfs(1, 0);
cout<<ans;
}
