#include <bits/stdc++.h>
using namespace std;
const int N = 5e4 + 2;
vector<vector<int> > g(N , vector<int>());
int ans = 0;
string all;
string walk = "";
bool good(string cur) {
string other = cur;
reverse(other.begin() , other.end());
return other == cur;
}
void dfs(int v , int p = -1) {
walk.push_back(all[v - 1]);
if (good(walk)) {
ans = max(ans , (int)walk.size());
}
for (int to : g[v]) {
if (to != p) {
dfs(to , v);
walk.pop_back();
}
}
}
int main() {
ios_base :: sync_with_stdio(0);
cin.tie(0) , cout.tie(0);
int n;
cin >> n;
cin >> all;
for (int i = 1; i < n; i++) {
int u , v;
cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
if (n <= 3000) {
//solve subtask 1
for (int i = 1; i <= n; i++) {
walk = "";
dfs(i);
}
cout << ans << '\n';
return 0;
}
return 0;
}
