#include <bits/stdc++.h>
using namespace std;
// Do you think you'll ever remember me someday, or will I just fade away from your memory?
#define LIFESUCK ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define ll long long
#define str string
#define mll map<ll, ll>
#define vll vector<ll>
#define pll pair<ll, ll>
#define fi first
#define se second
#define all(c) c.begin(), c.end()
#define pb push_back
#define debug cout << "I Love You\n";
#define fu(i, a, b) for (int i = a; i <= b; i++)
#define fd(i, b, a) for (int i = b; i >= a; i--)
#define Bitc(msk, j) ((msk >> j) & 1)
#define _log(x) 31 - __builtin_clz(x)
const ll Mod = 1e9 + 7;
const ll inf = (1ll << 30);
const ll lnf = (1ll << 60);
// When time passes and things change... will you still remember someone like me?
int64_t add(ll &a, ll b) {
a += b;
if (a >= Mod) a %= Mod;
while (a < 0) a += Mod;
return a;
}
int64_t mul(ll a, ll b) {
a = 1ll * a * b % Mod;
return a;
}
template <class X, class Y>
bool minimize(X &x, Y y) {
X eps = 1e-9;
if (x > y + eps) {
x = y;
return 1;
}
return 0;
}
template <class X, class Y>
bool maximize(X &x, Y y) {
X eps = 1e-9;
if (x + eps < y) {
x = y;
return 1;
}
return 0;
}
// I wonder… will I just become a distant memory to you one day?
#define mxn 200'007
ll n, len;
str s;
vll graph[mxn];
struct Edge{
ll u, v;
} edge[mxn];
namespace Love1 {
bool check () {
return (n <= 3000);
}
vector<char> t;
const ll base = 37;
ll f[3007][3007], g[3007][3007];
void dfs(ll u, ll p, ll *f, ll *g) {
for(auto &v: graph[u]) {
if(v == p) continue;
f[v] = f[u] + 1;
g[v] = (g[u] * base + s[v]) % Mod;
dfs(v, u, f, g);
}
}
void DreamyLove() {
ll sad = 1;
fu(u, 1, n) dfs(u, 0, f[u], g[u]);
fu(u, 1, n) fu(v, u + 1, n) if(g[u][v] == g[v][u]) maximize(sad, f[u][v] + 1);
cout << sad;
}
}
namespace Love2 {
bool check () {
ll cr = 0;
fu(i, 1, n) cr += (graph[i].size() == 1);
return (cr == 2);
}
ll f[mxn];
void DreamyLove () {
ll sad = 0;
ll rgh = 0, center = 0;
str t = "#";
for(auto&i: s) {
t += i;
t += '#';
}
ll n = t.size();
fu(i, 1, n) {
if(i < rgh) f[i] = min(rgh - i, f[2 * center - i]);
while(i - f[i] - 1 >= 0 && i + f[i] + 1 < n && t[i - f[i] - 1] == t[i + f[i] + 1]) f[i]++;
if(i + f[i] > rgh) center = i, rgh = i + f[i];
maximize(sad, f[i]);
}
cout << sad;
//
}
}
void lovesper(const ll &TestCase) {
cin >> n >> s;
len = s.size(); s = '#' + s;
fu(i, 2, n) {
ll u, v; cin >> u >> v;
graph[u].pb(v);
graph[v].pb(u);
edge[i] = {u, v};
}
if(Love1::check()) {
Love1::DreamyLove();
return;
}
if(Love2::check()) {
Love2::DreamyLove();
return;
}
}
signed main() {
LIFESUCK
#define name "lovesper"
// freopen(name".inp", "r", stdin);
// freopen(name".out", "w", stdout);
ll Test = 1;
// cin >> Test;
fu(i, 1, Test) {
lovesper(i);
if (i < Test) cout << '\n';
}
return 0;
}
