#include <bits/stdc++.h>
using namespace std;
int n;
vector<vector<int>> adjList;
vector<int> parent;
string isBased;
vector<int> dp;
int result = 0;
void depthFirstSearch(int u, int p)
{
int V = 0;
for (auto &v : adjList[u])
if (v != p)
{
depthFirstSearch(v, u);
dp[u] += dp[v];
if (dp[v] > dp[V])
V = v;
}
if (isBased[u] == '1')
{
result = max(dp[V] + 1, result);
dp[u] = max(1, dp[u] - 1);
}
result = max(dp[u], result);
}
int main()
{
// freopen("inp.txt", "r", stdin);
ios::sync_with_stdio(false);
cin >> n;
adjList.resize(n + 1);
parent.resize(n + 1);
for (int u, v, i = 1; i < n; i++)
{
cin >> u >> v;
adjList[u].emplace_back(v);
adjList[v].emplace_back(u);
}
cin >> isBased;
isBased = "!" + isBased;
dp.resize(n + 1);
depthFirstSearch(1, -1);
cout << result;
}
