#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define sz(x) (int)x.size()
#define ALL(v) v.begin(),v.end()
#define MASK(k) (1LL << (k))
#define BIT(x, i) (((x) >> (i)) & 1)
#define oo (ll)1e18
#define INF (ll)1e9
#define MOD (ll)(1e9 + 7)
using namespace std;
template<class T1, class T2>
bool maximize(T1 &a, T2 b){if(a < b){a = b; return true;} return false;}
template<class T1, class T2>
bool minimize(T1 &a, T2 b){if(a > b){a = b; return true;} return false;}
template<class T1, class T2>
void add(T1 &a, T2 b){a += b; if(a >= MOD) a -= MOD;}
template<class T1, class T2>
void sub(T1 &a, T2 b){a -= b; if(a < 0) a += MOD;}
template<class T>
void cps(T &v){sort(ALL(v)); v.resize(unique(ALL(v)) - v.begin());}
const int MAX = 5e4 + 10;
const int base = 311;
int N;
string s;
vector<int> adj[MAX];
int nChild[MAX], pw[MAX], height[MAX];
bool ok[MAX];
int ans = 0;
bool isDel[MAX];
void input(){
cin >> N;
cin >> s;
s = "0" + s;
for(int i=1; i<N; i++){
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
pw[0] = 1;
for(int i=1; i<=N; i++){
pw[i] = 1LL * pw[i - 1] * base % MOD;
}
}
namespace subtask1{
void dfs(int u, int p, int down, int up, int height){
down = (1LL * down * base + s[u]) % MOD;
up = (1LL * up + 1LL * s[u] * pw[height] % MOD) % MOD;
if(down == up) maximize(ans, height + 1);
for(int v: adj[u]) if(v != p){
dfs(v, u, down, up, height + 1);
}
}
void solve(){
pw[0] = 1;
for(int i=1; i<=N; i++){
pw[i] = 1LL * pw[i - 1] * base % MOD;
}
for(int i=1; i<=N; i++){
dfs(i, 0, 0, 0, 0);
}
cout << ans << '\n';
}
}
void countChild(int u, int p){
nChild[u] = 1;
for(int v: adj[u]) if(v != p && !isDel[v]){
countChild(v, u);
nChild[u] += nChild[v];
}
}
int centroid(int u, int p, int n){
for(int v: adj[u]) if(v != p && !isDel[v]){
if(nChild[v] * 2 > n) return centroid(v, u, n);
}
return u;
}
bool calc(int u, int p, int h, int down, int up, int len, unordered_map<int, int> &om){
h++;
down = (1LL * down * base + s[u]) % MOD;
up = (1LL * up + 1LL * s[u] * pw[h] % MOD) % MOD;
if(h + 1 > len) return false;
// cout << u << ' ' << h << ' ' << down << ' ' << up << '\n';
height[h + 1] = down;
if((h + 1) * 2 >= len){
int par = 2 * (h + 1) - len;
if(ok[par] && om.count((height[h + 1] - 1LL * height[par] * pw[h + 1 - par] % MOD + MOD * MOD) % MOD)){
return true;
}
}
if(down == up) ok[h + 1] = true;
bool ans = false;
for(int v: adj[u]) if(v != p && !isDel[v]){
ans = ans || calc(v, u, h, down, up, len, om);
}
ok[h + 1] = false;
return ans;
}
void update(int u, int p, int h, int down, int up, int len, unordered_map<int, int> &om){
h++;
down = (1LL * down * base + s[u]) % MOD;
up = (1LL * up + 1LL * s[u] * pw[h] % MOD) % MOD;
if(h + 1 > len) return;
om[down] = true;
for(int v: adj[u]) if(v != p && !isDel[v]){
update(v, u, h, down, up, len, om);
}
}
bool solve(int a, int len){
countChild(a, 0);
int u = centroid(a, 0, nChild[a]);
// cout << u << '\n';
unordered_map<int, int> om;
om[s[u]] = true;
for(int v: adj[u]) if(!isDel[v]){
ok[0] = true;
height[0] = 0;
if(calc(v, u, -1, 0, 0, len, om)) return true;
update(v, u, 0, s[u], s[u], len, om);
}
om.clear();
reverse(ALL(adj[u]));
for(int v: adj[u]) if(!isDel[v]){
ok[0] = ok[1] = true;
height[0] = 0;
height[1] = s[u];
if(calc(v, u, 0, s[u], s[u], len, om)) return true;
update(v, u, -1, 0, 0, len, om);
}
isDel[u] = true;
for(int v: adj[u]) if(!isDel[v]){
if(solve(v, len)) return true;
}
return false;
}
bool check(int k){
if(k == 0 || k == 1) return true;
memset(isDel, false, (N + 3) * sizeof(bool));
return solve(1, k);
}
int odd(){
int l = 0, r = N - N / 2;
while(l < r){
int m = (l + r) >> 1;
if((l + r) & 1) m++;
if(check(m * 2 + 1)){
l = m;
}
else{
r = m - 1;
}
}
return l * 2 + 1;
}
int even(){
int l = 0, r = N - N / 2;
while(l < r){
int m = (l + r) >> 1;
if((l + r) & 1) m++;
if(check(m * 2)){
l = m;
}
else{
r = m - 1;
}
}
return l * 2;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
input();
cout << max(odd(), even());
return 0;
}
