#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using T = tuple<ll, ll, ll>;
#define int long long
#define Base 41
#define sz(a) (int)a.size()
#define FOR(i, a, b) for ( int i = a ; i <= b ; i++ )
#define FORD(i, a, b) for (int i = b; i >= a; i --)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define REPD(i, n) for (int i = n - 1; i >= 0; --i)
#define all(x) x.begin() , x.end()
#define pii pair<int , int>
#define fi first
#define se second
#define Lg(x) 31 - __builtin_clz(x)
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int MAX = 5e4 + 5;
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void setupIO(){
#define name "Whisper"
//Phu Trong from Nguyen Tat Thanh High School for gifted student
srand(time(NULL));
cin.tie(nullptr)->sync_with_stdio(false); cout.tie(nullptr);
//freopen(name".inp", "r", stdin);
//freopen(name".out", "w", stdout);
cout << fixed << setprecision(10);
}
template <class X, class Y>
bool minimize(X &x, const 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, const Y &y){
X eps = 1e-9;
if (x + eps < y) {x = y; return 1;}
return 0;
}
int numNode;
string s;
vector<int> adj[MAX];
int sz[MAX], del[MAX];
void reSubize(int u, int p){
sz[u] = 1;
for (auto&v : adj[u]) if(v ^ p){
if (!del[v]){
reSubize(v, u); sz[u] += sz[v];
}
}
}
int getCentroid(int u, int p, int siz){
for (auto&v : adj[u]) if(v ^ p){
if (!del[v] && 2 * sz[v] > siz) return getCentroid(v, u, siz);
}
return u;
}
//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
int l = 0; bool found;
int Pow[MAX];
unordered_map<int, bool> f[MAX];
int maxDepth = 1;
char r;
void dfs(int u, int p, int dep, int up, int down, bool ok){
if (dep > l) return;
maximize(maxDepth, dep);
up = (up * Base + (s[u] - 'a' + 1)) % Mod;
down = (down + (s[u] - 'a' + 1) * Pow[dep - 1]) % Mod;
int val = ((down * Pow[l - dep] - up) + Mod) % Mod;
if (ok) f[dep][val] = 1;
else{
if (dep + 1 == l){
if ((down * Base + (r - 'a' + 1)) % Mod == up){
found = 1; return;
}
}
if (l > dep)
if (f[l - dep - 1].count(val)){
found = 1; return;
}
}
for (auto&v : adj[u]) if(v ^ p){
if (!del[v]){
dfs(v, u, dep + 1, up, down, ok);
if (found) return;
}
}
}
void decompose(int root){
reSubize(root, -1);
int siz = sz[root];
root = getCentroid(root, -1, siz);
r = s[root];
del[root] = 1;
maxDepth = 1;
for (auto&v : adj[root]) if(!del[v]){
dfs(v, root, 1, s[root] - 'a' + 1, 0, 0);
if (found) return;
dfs(v, root, 1, s[root] - 'a' + 1, 0, 1);
}
for (int i = 0; i <= maxDepth; ++i) f[i].clear();
for (auto&v : adj[root]) if(!del[v]){
decompose(v);
if (found) return;
}
}
bool check(int _l){
l = _l; found = false;
for (int i = 0; i <= l; ++i) f[i].clear();
for (int i = 1; i <= numNode; ++i) del[i] = 0;
decompose(1);
return found;
}
void Whisper(){
cin >> numNode >> s;
s = '@' + s;
for (int i = 1; i < numNode; ++i){
int u, v; cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
Pow[0] = 1;
for (int i = 1; i <= numNode; ++i){
Pow[i] = Pow[i - 1] * Base % Mod;
}
int ans = 1;
for (int i = 0; i < 2; ++i){
int lo = 0, hi = numNode / 2 + 1;
while (hi - lo > 1){
int mid = (lo + hi) >> 1;
if (check(2 * mid + i)) lo = mid;
else hi = mid;
}
maximize(ans, 2 * lo + i);
}
cout << ans;
}
signed main(){
setupIO();
int Test = 1;
// cin >> Test;
for ( int i = 1 ; i <= Test ; i++ ){
Whisper();
if (i < Test) cout << '\n';
}
}
