#include <bits/stdc++.h>
// #define int long long
using namespace std;
const int maxn = 50005;
const int base = 311, mod = 1e9 + 7;
int n;
string s;
vector <int> g[maxn];
int is_cen[maxn], sz[maxn];
int pw[maxn];
int add(int x, int y){
return (x + y) % mod;
}
int mul(int x, int y){
return 1LL * x * y % mod;
}
int sub(int x, int y){
return (x - y + mod) % mod;
}
void dfs_sz(int u, int p) {
sz[u] = 1;
for(int &v : g[u]) if(!is_cen[v] && v != p){
dfs_sz(v, u);
sz[u]+= sz[v];
}
}
int findcen(int u, int p, int big){
for(int &v : g[u]) if(!is_cen[v] && v != p){
if(sz[v] > big / 2) return findcen(v, u, big);
}
return u;
}
int ans = 1;
int hsh[maxn], rev_hsh[maxn], hei[maxn], par[maxn];
unordered_map <int, bool> mp[50005];
int len = 0, ok = 0;
int h[50005], ma = 0;
int getAns(int u, int p, int type){
h[u] = h[p] + 1;
ma = max(ma, h[u]);
if(h[u] > len) return 0;
hsh[u] = add(mul(hsh[p], base), s[u] - 'a' + 1);
rev_hsh[u] = add(mul(s[u] - 'a' + 1, pw[h[u] - 1]), rev_hsh[p]);
if(type == 0){
if(hsh[u] == rev_hsh[u] && h[u] + 1 >= len && (len % 2 == h[u] % 2)) return 1;
int curHash = (1LL * rev_hsh[u] * pw[len - h[u]] - hsh[u] + mod) % mod;
if(mp[len - h[u]].find(curHash) != mp[len - h[u]].end()) return 1;
} else{
int curHash = (1LL * rev_hsh[u] * pw[len - h[u]] - hsh[u] + mod) % mod;
mp[h[u]][curHash] = 1;
}
for(int &v : g[u]) if(!is_cen[v] && v != p){
if(getAns(v, u, type)) return 1;
}
return false;
}
int buildcen(int u){
dfs_sz(u, - 1);
int centroid = findcen(u, - 1, sz[u]);
is_cen[centroid] = true;
ma = 0;
for(int &v : g[centroid]){
if(is_cen[v]) continue;
h[centroid] = 1;
hsh[centroid] = rev_hsh[centroid] = (s[centroid] - 'a' + 1);
if(getAns(v, centroid, 0)) return 1;
h[centroid] = 0;
hsh[centroid] = rev_hsh[centroid] = 0;
getAns(v, centroid, 1);
}
for(int i = 0; i <= ma; i++) mp[i].clear();
for(int &v : g[centroid]){
if(!is_cen[v] && buildcen(v)) return true;
}
return false;
}
bool check(){
for(int i = 1; i <= n; i++) is_cen[i] = sz[i] = 0;
return buildcen(1);
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
// freopen("lampice.inp", "r", stdin);
// freopen("lampice.out", "w", stdout);
cin >> n >> s; s = "*" + s;
for(int i = 1; i < n; i++){
int u, v; cin >> u >> v;
g[u].push_back(v); g[v].push_back(u);
}
pw[0] = 1;
for(int i = 1; i <= n; i++){
pw[i] = 1LL * pw[i - 1] * base % mod;
}
int l = 1, r = n / 2;
while(l <= r){
int mid = (l + r) >> 1;
len = 2 * mid;
if(check()) ans = max(ans, len), l = mid + 1;
else r = mid - 1;
}
l = 0, r = (n - 1) / 2;
while(l <= r){
int mid = (l + r) >> 1;
len = 2 * mid + 1;
if(check()) ans = max(ans, len), l = mid + 1;
else r = mid - 1;
}
cout << ans;
return 0;
}
