#include <bits/stdc++.h>
#define TASK "lampice"
#define int long long
#define double long double
#define fi first
#define se second
#define pb push_back
#define ii pair<int, int>
#define vi vector<int>
#define vvi vector<vi>
#define vii vector<ii>
#define reset(f, x) memset(f, x, sizeof(f))
#define all(x) x.begin(), x.end()
#define sz(x) (long long)x.size()
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORD(i, b, a) for (int i = (b), _a = (a); i >= _a; --i)
#define FORV(v, H) for (auto &v: H)
#define __builtin_popcount __builtin_popcountll
#define BIT(mask, i) ((mask >> i) & 1ll)
#define MASK(i) (1ll << (i))
#define ONBIT(mask, i) (mask (1ll << (i)))
#define OFFBIT(mask, i) (mask &~ (1ll << (i)))
#define mid(l, r) ((l + r) >> 1)
#define left(id) (id << 1)
#define right(id) ((id << 1) 1)
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
#define UNIQUE(x) sort(all(x)); x.resize(distance(x.begin(), unique(all(x))))
#define BUG1(a) cout << a << '\n'
#define BUG2(a, b) cout << a << " " << b << '\n'
#define BUG3(a, b, c) cout << a << " " << b << " " << c << '\n'
#define BUG4(a, b, c, d) cout << a << " " << b << " " << c << " " << d << '\n'
#define BUG5(a, b, c, d, e) cout << a << " " << b << " " << c << " " << d << " " << e << '\n'
#define BUG6(a, b, c, d, e, f) cout << a << " " << b << " " << c << " " << d << " " << e << " " << f << '\n'
using namespace std;
template <class X, class Y> bool maximize(X &A, const Y &B){
if (A < B) return A = B, true;
return false;
}
template <class X, class Y> bool minimize(X &A, const Y &B){
if (A > B) return A = B, true;
return false;
}
const int oo = 1e18;
const int MOD = 1e9 + 7;
const int MAXN = 50000 + 5;
const int LOG = 16;
const int base = 31;
const int BLOCK = 317;
const int dx[] = {0, 0, 1, 0, -1};
const int dy[] = {0, 1, 0, -1, 0};
int N;
string S;
vi G[MAXN];
int len, mx, a[MAXN], sz[MAXN], pw[MAXN];
bool del[MAXN];
unordered_set<int> f[MAXN];
vii L;
namespace Sub4{
int DFS(int u, int parent){
sz[u] = 1;
FORV(v, G[u]){
if (v == parent || del[v]) continue;
DFS(v, u);
sz[u] += sz[v];
}
return sz[u];
}
int FIND(int u, int parent, int Size){
FORV(v, G[u]){
if (v == parent || del[v]) continue;
if (sz[v] > Size) return FIND(v, u, Size);
}
return u;
}
bool dfs(int u, int parent, int depth, int down, int up){
if (depth > len) return 0;
if (parent) down = (down * base + a[u]) % MOD;
up = (up + a[u] * pw[depth - 1]) % MOD;
int x = (up * pw[len - depth] - down + MOD) % MOD;
if (!parent) f[depth].insert(x);
if (f[len - depth + 1].count(x)) return 1;
FORV(v, G[u]){
if (v == parent || del[v]) continue;
if (!parent) L.clear();
if (dfs(v, u, depth + 1, down, up)) return 1;
if (!parent){
for(ii l : L) f[l.fi].insert(l.se);
}
}
maximize(mx, depth);
L.push_back({depth, x});
return 0;
}
bool solve(int u, int last_centroid){
int Size = DFS(u, last_centroid);
int centroid = FIND(u, last_centroid, Size >> 1ll);
if (dfs(centroid, 0, 1, 0, 0)) return 1;
FOR(i, 1, mx) f[i].clear();
mx = 0;
del[centroid] = 1;
FORV(v, G[centroid]){
if (v == last_centroid || del[v]) continue;
if (solve(v, centroid)) return 1;
}
return 0;
}
bool check(int mid){
len = mid;
FOR(i, 1, N){
del[i] = 0;
f[i].clear();
}
return solve(1, 0);
}
void SOLVE(){
int l = -1, r = N + 1, ans = 0;
while (r - l > 1){
int mid = mid(l, r);
if (mid & 1){
if (check(mid)) l = mid;
else r = mid;
} else{
if (check(mid + 1)) l = mid + 1;
else r = mid;
}
}
maximize(ans, l);
l = -1; r = N + 1;
while (r - l > 1){
int mid = mid(l, r);
if (mid & 1){
if (check(mid + 1)) l = mid + 1;
else r = mid;
} else{
if (check(mid)) l = mid;
else r = mid;
}
}
maximize(ans, l);
cout << ans << '\n';
}
}
void PROCESS(){
Sub4::SOLVE();
}
main(){
if (fopen(TASK".inp", "r")){
freopen(TASK".inp", "r", stdin);
freopen(TASK".out", "w", stdout);
}
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin >> N >> S;
S = " " + S;
pw[0] = 1;
FOR(u, 1, N){
a[u] = S[u] - 'a' + 1;
pw[u] = (pw[u - 1] * base) % MOD;
}
FOR(i, 1, N - 1){
int u, v;
cin >> u >> v;
G[u].push_back(v);
G[v].push_back(u);
}
PROCESS();
return 0;
}
/*
___ __ ___ _______ ___ ___ ________ ___ ________ ___ ___ ___ ___ ___ ___
\ \\ \ |\ \|\ ___ \ |\ \|\ \ |\ ____\|\ \|\ __ \ |\ \|\ \|\ \|\ \ |\ \ / / |
\ \ \/ /|\ \ \ \ __/|\ \ \\\ \ \ \ \___|\ \ \ \ \|\ \ \ \ \\\ \ \ \\\ \ \ \ \/ / /
\ \ ___ \ \ \ \ \_|/_\ \ \\\ \ \ \ \ __\ \ \ \ __ \ \ \ __ \ \ \\\ \ \ \ / /
\ \ \\ \ \ \ \ \ \_|\ \ \ \\\ \ \ \ \|\ \ \ \ \ \ \ \ \ \ \ \ \ \ \\\ \ \/ / /
\ \__\\ \__\ \__\ \_______\ \_______\ \ \_______\ \__\ \__\ \__\ \ \__\ \__\ \_______\__/ / /
\|__| \|__|\|__|\|_______|\|_______| \|_______|\|__|\|__|\|__| \|__|\|__|\|_______|\___/ /
\|___|/
Author: Kieu Gia Huy a.k.a kiwi
From: C.H.V with luv <3
...
*/
