#include <bits/stdc++.h>
using namespace std;
#define x first
#define y second
typedef pair<long long, long long> hash_t;
hash_t operator+(hash_t a, hash_t b) { return {a.x + b.x, a.y + b.y}; }
hash_t operator*(hash_t a, hash_t b) { return {a.x * b.x, a.y * b.y}; }
hash_t operator+(hash_t a, char b) { return {a.x + b, a.y + b}; }
hash_t operator*(hash_t a, char b) { return {a.x * b, a.y * b}; }
const int MAXN = 100100;
const hash_t BASE = {31337, 10007};
int n;
char input[MAXN];
vector<int> adj[MAXN];
hash_t P[MAXN];
int ans = 1;
void rec(int x, int prev = -1, hash_t down = {0, 0}, hash_t up = {0, 0}, int len = 1) {
down = down * BASE + input[x];
up = up + P[len - 1] * input[x];
if (up == down && len > ans)
ans = len;
for (int y : adj[x]) {
if (y == prev) continue;
rec(y, x, down, up, len + 1);
}
}
int main(void) {
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);
}
P[0] = {1, 1};
for (int i = 1; i < n; ++i)
P[i] = P[i - 1] * BASE;
for (int i = 0; i < n; ++i)
rec(i);
cout << ans << endl;
return 0;
}
