// Om Namah Shivaya
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)
template<typename T>
void amin(T &a, T b) {
a = min(a, b);
}
template<typename T>
void amax(T &a, T b) {
a = max(a, b);
}
#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif
/*
read edi long time ago, dont exactly remember the approach in the edi
*/
const int MOD = 1e9 + 7;
const int N = 2e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
vector<ll> adj[N];
vector<ll> a(N);
ll dp[N][2];
void dfs(ll u, ll p, ll r){
rep(j,2) dp[u][j] = 0;
ll dp1[5], dp2[5];
memset(dp1,0,sizeof dp1);
memset(dp2,0,sizeof dp2);
trav(v,adj[u]){
if(v == p) conts;
dfs(v,u,r);
memset(dp2,0,sizeof dp2);
rep(j,3){
rep(k,2){
ll j2 = min(j+k,2);
amax(dp2[j2],dp1[j]+dp[v][k]);
}
}
rep(j,5) dp1[j] = dp2[j];
}
if(u != r){
dp[u][0] = dp1[0];
dp[u][1] = max(dp1[1],dp1[2]);
if(a[u]){
dp[u][1]--;
amax(dp[u][1],dp[u][0]+1);
}
}
else{
dp[u][0] = dp1[0];
dp[u][1] = max(dp1[1]+1,dp1[2]-1);
}
rep(j,2){
amax(dp[u][j],0ll);
}
}
void solve(int test_case)
{
ll n; cin >> n;
rep1(i,n-1){
ll u,v; cin >> u >> v;
adj[u].pb(v), adj[v].pb(u);
}
rep1(i,n){
char ch; cin >> ch;
a[i] = ch-'0';
}
ll ans = 0;
rep1(r,n){
if(!a[r]) conts;
// if(r != 2) conts;
dfs(r,-1,r);
amax(ans,dp[r][1]);
}
cout << ans << endl;
}
int main()
{
fastio;
int t = 1;
// cin >> t;
rep1(i, t) {
solve(i);
}
return 0;
}
