#include <bits/stdc++.h>
#define L(i, j, k) for(int i = (j); i <= (k); i++)
#define R(i, j, k) for(int i = (j); i >= (k); i--)
#define all(x) x.begin(), x.end()
#define sz(a) ((int) a.size())
#define pb push_back
#define fst first
#define snd second
using namespace std;
typedef long long ll;
const int MAXN=2e5+5,INF=1e9;
vector<int>adj[MAXN];
bool gen[MAXN],on[MAXN],br[MAXN];
void dfs(int u,int p,vector<int>&nodes){
if(on[u]&&sz(nodes)>2){
L(i,1,sz(nodes)-2){
br[nodes[i]]=true;
}
}
for(auto v:adj[u]){
if(v==p)continue;
if(gen[v])nodes.pb(v);
dfs(v,u,nodes);
if(gen[v])nodes.pop_back();
}
}
int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;cin>>n;
L(i,0,n-2){
int a,b;cin>>a>>b;
a--;b--;
adj[a].pb(b);
adj[b].pb(a);
}
string s;cin>>s;
vector<int>v;
L(i,0,n-1)if(s[i]=='1'){
gen[i]=true;
v.pb(i);
}
int m=sz(v),ans=-INF;
L(mask,0,(1<<m)-1){
L(i,0,m-1){
if((1<<i)&mask){
on[v[i]]=true;
root=v[i];
}
}
L(i,0,m-1){
vector<int>a(1,v[i]);
if((1<<i)&mask)dfs(v[i],-1,a);
}
int cur=0;
L(i,0,m-1){
if(br[v[i]])cur--;
else if(!br[v[i]]&&(1<<i)&mask)cur++;
}
ans=max(ans,cur);
L(i,0,m-1)on[v[i]]=br[v[i]]=false;
}
cout<<ans<<endl;
}
