#pragma GCC optimize("O3", "unroll-loops") // "Ofast"
#pragma GCC target("avx2", "bmi", "bmi2", "lzcnt", "popcnt")
#include <bits/stdc++.h>
//#define int long long
#define vt vector
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define ff first
#define ss second
#define dbg(x) cerr << #x << " = " << x << '\n'
#define bit(x, i) ((x) >> (i) & 1)
using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using vvt = vt< vt<ll> >;
const int N = 1e6 + 5, mod = 1e9 + 7, B = 500;
const ll inf = 1e18 + 7, LIM = (1ll << 60);
const ld eps = 1e-6;
int n, ans;
string s;
vt<int> g[N];
vt<char> c;
int get () {
int res = 0;
for (int i = 0; i < sz(c); i++) {
int l = i - 1, r = i + 1;
while (l >= 0 && r < sz(c)) {
if (c[l] == c[r]) l--, r++;
else break;
}
l++, r--;
res = max(res, r - l + 1);
l = i - 1, r = i;
while (l >= 0 && r < sz(c)) {
if (c[l] == c[r]) l--, r++;
else break;
}
l++, r--;
res = max(res, r - l + 1);
}
return res;
}
void dfs (int v, int p = -1) {
c.pb(s[v]);
bool ok = 0;
for (auto to: g[v]) {
if (to != p) {
ok = 1;
dfs(to, v);
}
}
if (!ok) ans = max(ans, get());
c.pop_back();
}
bool pal (vt<char> &c) {
vt<char> nc = c;
reverse(all(nc));
return (c == nc);
}
void df (int v, int p = -1) {
c.pb(s[v]);
if (pal(c)) ans = max(ans, sz(c));
for (auto to: g[v]) {
if (to != p) df(to, v);
}
c.pop_back();
}
void solve () {
cin >> n >> s;
s = ' ' + s;
for (int i = 1; i < n; i++) {
int x, y;
cin >> x >> y;
g[x].pb(y);
g[y].pb(x);
}
if (n <= 100) {
for (int i = 1; i <= n; i++) c.clear(), df(i);
cout << ans;
return;
}
for (int i = 1; i <= n; i++) {
if (sz(g[i]) == 1) c.clear(), dfs(i);
}
cout << ans;
cout << '\n';
}
bool testcases = 0;
signed main() {
#ifdef ONLINE_JUDGE
freopen(".in", "r", stdin);
freopen(".out", "w", stdout);
#endif
cin.tie(0) -> sync_with_stdio(0);
int test = 1;
if (testcases) cin >> test;
for (int cs = 1; cs <= test; cs++) {
solve();
}
}
