#include <bits/stdc++.h>
using namespace std;
template<typename T>
void out(T x) { cout << x << endl; exit(0); }
#define watch(x) cout << (#x) << " is " << (x) << endl
using ll = long long;
const ll mod = 1e9+7;
const int maxn = 1e6 + 5;
int n;
vector<int> g[maxn];
string s;
set<int> broken;
int x,y;
bool dfs(int at, int p) {
if (at==y) return true;
for (int to: g[at]) {
if (to==p) continue;
if (dfs(to,at)) {
if (s[at]=='1' && at!=x) {
broken.insert(at);
}
return true;
}
}
return false;
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>>n;
for (int i=0; i<n-1; i++) {
int u,v; cin>>u>>v;
--u; --v;
g[u].push_back(v);
g[v].push_back(u);
}
cin>>s;
int best = 0;
for (int mask=0; mask<1<<n; mask++) {
vector<int> v;
bool ok = true;
for (int j=0; j<n && ok; j++) {
if (mask>>j&1) {
if (s[j]=='0') ok=false;
v.push_back(j);
}
}
if (!ok) continue;
broken.clear();
for (int i=0; i<int(v.size()); i++) {
for (int j=i+1; j<int(v.size()); j++) {
x=v[i]; y=v[j];
dfs(v[i],-1);
}
}
int res = 0;
for (int x: v) {
if (!broken.count(x)) res++;
}
res -= int(broken.size());
best = max(best, res);
}
cout<<best<<endl;
return 0;
}
