#include<bits/stdc++.h>
using namespace std;
#define all(fl) fl.begin(),fl.end()
#define pb push_back
#define fi first
#define se second
#define for1(i,j,k) for(int i=j;i<=k;i++)
#define for2(i,j,k) for(int i=j;i>=k;i--)
#define for3(i,j,k,l) for(int i=j;i<=k;i+=l)
#define lb lower_bound
#define ub upper_bound
#define sz(a) (int)a.size()
#define pii pair<int,int>
#define pli pair<long long,int>
#define gcd __gcd
#define lcm(x,y) x*y/__gcd(x,y)
#define pil pair<int,long long>
vector<int>a[200009];
int f[200009];
string s;
int ans=0;
void dfs(int u,int par){
if (s[u]=='1'){
f[u]=1;
}
int sum=0;
for (auto v:a[u]){
if (v==par)continue;
dfs(v,u);
if (s[u]=='1'){
ans=max(ans,f[v]+1);
}
sum+=f[v];
}
if (s[u]=='1')sum--;
f[u]=max(f[u],sum);
ans=max(ans,f[u]);
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
//freopen("temp.INP","r",stdin);
//freopen("temp.OUT","w",stdout);
int n;
cin>>n;
for1(i,1,n-1){
int u,v;
cin>>u>>v;
a[u].pb(v);
a[v].pb(u);
}
cin>>s;
s=" "+s;
dfs(1,0);
cout<<ans;
}
