#include <bits/stdc++.h>
#include <iostream>
#include <cstdlib>
#include <iomanip>
#include <vector>
#include <cmath>
#include <assert.h>
#include <ctime>
#include <math.h>
#include <queue>
#include <string>
#include <numeric>
#include <fstream>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <stack>
#include <random>
#include <list>
#include <bitset>
#include <algorithm>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
#define pll pair<ll, ll>
#define pii pair<int, int>
#define pdd pair<ld, ld>
#define ff first
#define ss second
#define all(v) v.begin(),v.end()
typedef tree<
pii,
null_type,
less<pii>,
rb_tree_tag,
tree_order_statistics_node_update> ordset;
#pragma GCC optimize("-O3")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-Os")
ll INF = 2e18;
//mt19937 gen(time(0));
ll gcd(ll n, ll m){
while(n != 0 && m != 0){
if(n > m) n %= m;
else m %= n;
}
return n + m;
}
ll lcm(ll n, ll m){
ll nod = gcd(n, m);
return n / nod * m;
}
ll mod = 1e9 + 7;
ll binpow(ll n, ll m){
if(m == 0) return 1;
if(m % 2ll == 1) {
return (binpow(n, m - 1ll) * 1ll * n) % mod;
}
ll b = binpow(n, m / 2);
return (b * 1ll * b) % mod;
}
vector<vector<int>> a;
vector<int> dp;
int ans = 0;
string s;
void dfs(int v, int p){
int mx = 0;
for(int u : a[v]){
if(u == p) continue;
dfs(u, v);
dp[v] += dp[u];
mx = max(mx, dp[u]);
}
if(s[v] == '0'){
ans = max(ans, dp[v]);
return;
}
ans = max(ans, mx + 1);
dp[v] = max(1, dp[v] - 1);
ans = max(ans, dp[v]);
}
void solve(){
int n;
cin >> n;
a.resize(n);
dp.resize(n, 0);
for(int i = 0; i < n - 1; i++){
int u, v;
cin >> u >> v;
u--; v--;
a[u].push_back(v);
a[v].push_back(u);
}
cin >> s;
int cnt = 0;
for(int i = 0; i < n; i++) if(s[i] == '1') cnt++;
ans = min(cnt, 2);
dfs(0, -1);
cout << ans << '\n';
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int tt;
//cin >> tt;
tt = 1;
while (tt--) {
solve();
}
return 0;
}
