// Code by Parsa Eslami
#include <bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define pll pair<ll,ll>
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define FORR(i,a,b) for(int i=a;i>=b;i--)
#define maxm(a,b) a=max(a,b)
#define minm(a,b) a=min(a,b)
#define all(x) x.begin(),x.end()
#define SZ(x) ((int)x.size())
#define bit(i,j) ((j>>i)&1)
#define pb push_back
#define lc 2id
#define rc 2id+1
#define dmid int mid=(r+l)/2
#define err(x) cerr<#x<<" : "<<x<<'\n'
using namespace std;
const int N=16+1;
int get(){
int x; cin>>x; return x;
}
vector<int> adj[N];
int sz[N];
bool gen[N];
bool on[N];
int n;
void dfs(int v,int p){
sz[v]=on[v];
for(int u:adj[v]) if(u!=p) dfs(u,v),sz[v]+=sz[u];
}
int check(){
FOR(i,1,n) if(!gen[i]&&on[i]) return 0;
int rt=0;
FOR(i,1,n){
dfs(i,i);
int y=0;
for(int u:adj[i]) y+=(sz[u]>0);
if(on[i]&&y>1) return 0;
if(gen[i]&&y>1) rt--;
if(on[i]) rt++;
}
return rt;
}
int32_t main(){
iostream::sync_with_stdio(0); cin.tie(0);
n=get();
FOR(i,1,n-1){
int u=get(),v=get();
adj[u].pb(v);
adj[v].pb(u);
}
string s; cin>>s;
FOR(i,0,n-1) gen[i+1]=s[i]-'0';
int ot=0;
FOR(msk,0,(1<<n)-1){
FOR(j,0,n-1) on[j+1]=bit(j,msk);
maxm(ot,check());
}
cout<<ot<<'\n';
return 0;
}
