#include <bits/stdc++.h>
#define rep(i,l,r) for (int i = l; i < r; i++)
#define pb push_back
using namespace std;
constexpr int N = 2e5+10;
int dp[N][2],n;
vector<int> adj[N];
string s;
void dfs(int v,int p){
for (int u : adj[v]){
if (u != p){
dfs(u,v);
}
}
if (s[v-1] == '0'){
int su = 0;
for (int u : adj[v]){
if (u == p) continue;
su += dp[u][1];
dp[v][0] = max(dp[v][0],dp[u][0]);
}
dp[v][0] = max(dp[v][0],su);
dp[v][1] = su;
return;
}
dp[v][0] = dp[v][1] = 1;
int su = 0;
for (int u : adj[v]){
if (u == p) continue;
dp[v][0] = max({dp[v][0],dp[u][0],1+dp[u][1]});
su += dp[u][1];
}
dp[v][0] = max(dp[v][0],su-1);
dp[v][1] = max(dp[v][1],su-1);
}
int main(){
ios_base :: sync_with_stdio(0); cin.tie(0);
cin >> n;
rep(i,1,n){
int u,v;
cin >> u >> v;
adj[u].pb(v);
adj[v].pb(u);
}
cin >> s;
dfs(1,0);
cout << dp[1][0];
}
