#include <bits/stdc++.h>
using namespace std;
#define f first
#define s second
typedef long long ll;
typedef pair<int,int> pi;
const int large = 2e5+5;
int n, ans = 0;
vector<bool> power;
vector<int> edges[large];
vector<int> dp;
void dfs(int node, int par){
int cans = 0;
if(power[node]) cans = 1;
int best = 0;
int csum = 0;
for(auto &a: edges[node]){
if(a == par) continue;
dfs(a,node);
csum += dp[a];
best = max(best,dp[a]);
}
if(power[node]){
ans = max(ans,best+1);
csum--;
}
cans = max(cans,csum);
ans = max(ans,cans);
dp[node] = cans;
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n;
dp.resize(n+1); power.resize(n+1);
for(int i = 0; i < n-1; i++){
int u,v; cin >> u >> v;
edges[u].push_back(v);
edges[v].push_back(u);
}
for(int i = 1; i <= n; i++){
char a; cin >> a;
if(a == '1') power[i] = 1;
}
dfs(1,0);
cout << ans << "\n";
return 0;
}
