#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pii;
#define all(x) x.begin(), x.end()
#define sz(x) ((int) ((x).size()))
#define pb push_back
#define F first
#define S second
#define FIO ios_base::sync_with_stdio(false); cin.tie(0)
const int N = 2e5 + 10;
int n;
vector<int> adj[N];
int par[N];
int dp[N][2];
string s;
void dfs(int node) {
for (int x : adj[node]) {
if (par[node] == x) continue;
par[x] = node;
dfs(x);
}
}
int run(int node, bool on) {
if (dp[node][on] != -1) return dp[node][on];
int ans = 0;
if (s[node - 1] == '1') {
ans = 1;
if (on == 0) {
for (int x : adj[node]) {
if (par[node] == x) continue;
ans = max(ans, run(x, 0));
ans = max(ans, run(x, 1) + 1);
}
}
int sum = 0;
for (int x : adj[node]) {
if (par[node] == x) continue;
sum += run(x, 1);
}
ans = max(sum - 1, ans);
} else {
int sum = 0;
for (int x : adj[node]) {
if (par[node] == x) continue;
sum += run(x, 1);
}
ans = max(sum, ans);
for (int x : adj[node]) {
if (par[node] == x) continue;
ans = max(ans, run(x, 0));
}
}
dp[node][on] = ans;
return dp[node][on];
}
int main() {
FIO;
memset(dp, -1, sizeof dp);
cin >> n;
for (int i = 0; i < n - 1; i++) {
int a, b;
cin >> a >> b;
adj[a].pb(b);
adj[b].pb(a);
}
cin >> s;
dfs(1);
cout << run(1, 0) << endl;
return 0;
}
