#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pld pair<ld, ld>
#define pb push_back
#define fi first
#define se second
#define debug(x) cout << #x << " => " << x << endl
#define all(x) x.begin(),x.end()
vector<int> adj[200010];
string s;
int ans;
int dp[200010];
void dfs(int u,int p)
{
int sum=0,mx=0;
for(auto i : adj[u])
{
if(i!=p)
{
dfs(i,u);
sum+=dp[i];
mx=max(mx,dp[i]);
}
}
if(s[u-1]=='0') dp[u]=sum;
else
{
dp[u]=max(1,sum-1);
ans=max(ans,mx+1);
}
ans=max(ans,dp[u]);
}
int main()
{
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
int n;cin>>n;
for(int i=1;i<n;i++)
{
int u,v;cin>>u>>v;
adj[u].pb(v);
adj[v].pb(u);
}
cin>>s;
dfs(1,-1);
cout<<ans;
return 0;
}
