#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
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();
}
}
}
//manacher
int getMaxPalindromic(string text) {
int N = text.size();
if(N == 0)
return 0;
N = 2*N + 1; //Position count
int L[N]; //LPS Length Array
L[0] = 0;
L[1] = 1;
int C = 1; //centerPosition
int R = 2; //centerRightPosition
int i = 0; //currentRightPosition
int iMirror; //currentLeftPosition
int maxLPSLength = 0;
int maxLPSCenterPosition = 0;
int start = -1;
int end = -1;
int diff = -1;
for (i = 2; i < N; i++)
{
iMirror = 2*C-i;
L[i] = 0;
diff = R - i;
if(diff > 0)
L[i] = min(L[iMirror], diff);
while ( ((i + L[i]) < N && (i - L[i]) > 0) &&
( ((i + L[i] + 1) % 2 == 0) ||
(text[(i + L[i] + 1)/2] == text[(i - L[i] - 1)/2] )))
{
L[i]++;
}
if(L[i] > maxLPSLength)
{
maxLPSLength = L[i];
maxLPSCenterPosition = i;
}
if (i + L[i] > R)
{
C = i;
R = i + L[i];
}
}
start = (maxLPSCenterPosition - maxLPSLength)/2;
end = start + maxLPSLength - 1;
return end - start + 1;
}
vector<bool> lf(N , false);
void dfs1(int v , int p = -1) {
walk.push_back(all[v - 1]);
if (lf[v]) {
int cur = getMaxPalindromic(walk);
ans = max(ans , cur);
}
for (int to : g[v]) {
if (to != p) {
dfs1(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;
bool subtask2 = true;
for (int i = 1; i < n; i++) {
int u , v;
cin >> u >> v;
if (u + 1 != v) {
subtask2 = false;
}
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;
}
if (subtask2) {
//solve subtask 2
cout << getMaxPalindromic(all) << '\n';
return 0;
}
vector<int> leafs;
for (int i = 1; i <= n; i++) {
if ((int)g[i].size() == 1) {
leafs.push_back(i);
lf[i] = true;
}
}
for (int i = 0; i < (int)leafs.size(); i++) {
walk = "";
dfs1(leafs[i]);
}
cout << ans << '\n';
return 0;
}
