#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 200000;
int n;
ll dp[N][3];
string s;
vector<int> adj[N];
void dfs(int x, int pr) {
dp[x][0] = INT_MIN;
if(s[x] == '1')
dp[x][0] = 1;
ll val1 = INT_MIN, val3 = 0;
if(s[x] == '1')
val1 = 1;
ll v2 = 0;
for(auto e : adj[x]) if(e != pr) {
dfs(e, x);
if(dp[x][0] != INT_MIN)
dp[x][0] = 1 + max(dp[x][0] - 1, dp[e][2]);
v2 += max(0LL, dp[e][2]);
val3 = max(val3, dp[e][1]);
}
dp[x][1] = val1;
dp[x][1] = max(dp[x][1], val3);
dp[x][2] = val1;
dp[x][2] = max(dp[x][2], v2 - (s[x] == '1'));
dp[x][2] = max(dp[x][2], 0LL);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
for(int i = 0;i < n-1;i ++) {
int x, y; cin >> x >> y;
x --,y --;
adj[x].push_back(y);
adj[y].push_back(x);
}
cin >> s;
dfs(0, -1);
ll ans = 0;
for(int i = 0;i < n;i ++) {
// cerr << dp[i][0] << ' ' << dp[i][1] << ' ' << dp[i][2] << '\n';
ans = max(ans, dp[i][0]);
ans = max(ans, dp[i][1]);
ans = max(ans, dp[i][2]);
}
cout << ans << '\n';
}
