#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define ld long double
#define pb push_back
#define all(v) begin(v), end(v)
#define pll pair<ll, ll>
#define fi first
#define se second
#define vll vector<ll>
#define mll map<ll, ll>
mt19937_64 rng(chrono::high_resolution_clock().now().time_since_epoch().count());
const ll N = 5e4 + 6, inf = 1e18 + 7, mod = 1e9 + 7;
ll n, m, k, q, ans, a[N], base = 29, pw[N], del[N], sz[N];
vll adj[N];
string s;
unordered_map<ll, bool> mp[N];
void dfs_sz(ll p, ll u) {
sz[u] = 1;
for (ll v : adj[u]) {
if (v == p || del[v]) continue;
dfs_sz(u, v);
sz[u] += sz[v];
}
}
ll centroid(ll p, ll u, ll n) {
for (ll v : adj[u]) {
if (v != p && sz[v] > n/2 && !del[v]) return centroid(u, v, n);
}
return u;
}
ll res = 0, mx_dep = 0;
void dfs_hsh(ll p, ll u, ll len, ll dep, ll h1, ll h2) {
if (dep >= len) return;
mx_dep = max(mx_dep, dep);
ll x = (h1 * pw[len-dep-1] - h2 + mod) % mod;
//cout << u << " " << dep << " " << x << "\n";
if (p == -1) mp[dep][x] = 1; //update root
if (mp[len-dep-1].count(x)) {
res = 1;
return;
}
for (ll v : adj[u]) {
if (v == p || del[v]) continue;
ll t1 = ((s[v] - 'a' + 1) * base + h1) % mod;
ll t2 = (h2 * base + s[v] - 'a' + 1) % mod;
dfs_hsh(u, v, len, dep+1, t1, t2);
}
mp[dep][x] = 1;
}
void decomp(ll u) {
//cout << "subtree " << u << "\n";
dfs_sz(-1, u);
ll root = centroid(-1, u, sz[u]);
//cout << "centroid " << root << "\n";
ll l = 1, r = n;
while (l <= r) {
ll mid = (l+r) / 2, len = mid*2;
//cout << "LEN " << len << "\n";
for (int i = 0; i <= mx_dep; ++i) mp[i].clear();
res = mx_dep = 0;
dfs_hsh(-1, root, len, 0, s[root] - 'a' + 1, 0);
if (res) ans = max(ans, len), l = mid+1;
else r = mid-1;
}
l = 1, r = n;
while (l <= r) {
ll mid = (l+r) / 2, len = mid*2+1;
//cout << "LEN " << len << "\n";
for (int i = 0; i <= mx_dep; ++i) mp[i].clear();
for (int i = 0; i <= mx_dep; ++i) mp[i].clear();
res = mx_dep = 0;
dfs_hsh(-1, root, len, 0, s[root] - 'a' + 1, 0);
if (res) ans = max(ans, len), l = mid+1;
else r = mid-1;
}
//cout << "ans " << ans << "\n\n";
del[root] = 1;
for (ll v : adj[root]) {
if (!del[v]) decomp(v);
}
}
void solve() {
cin >> n >> s;
s = " " + s;
pw[0] = 1;
for (int i = 1; i <= n; ++i) pw[i] = pw[i-1] * base % mod;
for (int i = 1; i < n; ++i) {
ll x, y;
cin >> x >> y;
adj[x].pb(y);
adj[y].pb(x);
}
ans = 1;
decomp(1);
cout << ans;
return;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
if (fopen(".INP", "r")) {
freopen(".INP", "r", stdin);
freopen(".OUT", "w", stdout);
}
ll tc = 1;
// cin >> tc;
while (tc--) {
solve();
}
return 0;
}
