#include <bits/stdc++.h>
using namespace std;
const int MAXN = 50010;
int n;
char input[MAXN];
vector<int> adj[MAXN];
int stk_sz = 1;
char stk[2 * MAXN];
int pivot = 0;
int ans = 1;
int manacher() {
static int rad[2 * MAXN];
int x = 0;
for (int i = 1; i < stk_sz; ++i) {
int &r = rad[i] = 0;
if (i <= x + rad[x])
r = min(rad[2 * x - i], x + rad[x] - i);
while (i - r - 1 >= 0 && i + r + 1 < stk_sz &&
stk[i - r - 1] == stk[i + r + 1]) ++r;
if (i + r >= x + rad[x]) x = i;
}
int ret = 0;
for (int i = 0; i < stk_sz; ++i)
if (rad[i] > ret)
ret = rad[i];
return ret;
}
void dfs(int x, int prev = -1) {
stk[stk_sz++] = input[x];
stk[stk_sz++] = '*';
if (adj[x].size() == 1 && x < pivot)
ans = max(ans, manacher());
for (int y : adj[x]) {
if (y == prev) continue;
dfs(y, x);
}
stk_sz -= 2;
}
int main(void) {
ios_base::sync_with_stdio(false);
cin >> n;
cin >> input;
for (int i = 0; i < n - 1; ++i) {
int u, v;
cin >> u >> v;
u--; v--;
adj[u].push_back(v);
adj[v].push_back(u);
}
stk[0] = '*';
for (int i = 0; i < n; ++i) {
if (adj[i].size() != 1)
continue;
pivot = i;
dfs(i);
}
cout << ans << endl;
return 0;
}
