#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvl = vector<vll>;
using vb = vector<bool>;
using pll = pair<ll,ll>;
using vpl = vector<pll>;
using vvp = vector<vpl>;
#define f first
#define s second
#define pb push_back
#define all(v) v.begin(),v.end()
vvl g;
vb gen;
vll dp0, dp1;
ll ans = 0;
void dfs(ll cur, ll par){
if(!gen[cur]){
for(ll i:g[cur]){
if(i==par)continue;
dfs(i, cur);
dp0[cur]+=dp0[i];
dp1[cur] = max(dp1[cur], dp1[i]);
}
}
else{
ll mx=0;
for(ll i:g[cur]){
if(i==par)continue;
dfs(i, cur);
dp0[cur]+=dp0[i];
dp1[cur] = max(dp1[cur], dp1[i]);
mx = max(mx, dp0[i]);
}
dp0[cur] = max(dp0[cur]-1, 1ll);
dp1[cur] = max(dp1[cur]-1, mx+1);
}
ans = max(ans, max(dp0[cur], dp1[cur]));
}
int main(){
ios_base::sync_with_stdio(0);cin.tie(NULL);
ll n, a, b; cin >> n;
g = vvl(n+1, vll());
gen = vb(n+1);
dp0=dp1=vll(n+1);
for(ll i = 0; i < n-1; ++i){
cin >> a >> b;
g[a].pb(b);
g[b].pb(a);
}
string s;
cin >> s;
for(ll i = 1; i <= n; ++i)if(s[i-1]=='1')gen[i]=1;
dfs(1,0);
cout << ans;
}
