#include<bits/stdc++.h>
using namespace std;
#define task "noel"
#define ii pair<int,int>
#define fi first
#define se second
#define int long long
#define ll long long
#define ld double
#define mp make_pair
#define lg2 30
#define iii pair<int,ii>
#define iiii pair<ii,ii>
#define fii fi.fi
#define fis fi.se3
#define sfi se.fi
#define see se.se
#define base 29
int dx[]={0LL,0LL,1,-1,1,1,-1,-1};
int dy[]={1,-1,0LL,0LL,1,-1,1,-1};
const int maxn=5e4+1;
const int mod=1e9+7;
int h[maxn],n;
char s[maxn];
vector<int>a[maxn];
void dfs(int u,int cha)
{
for(int v:a[u])
{
if(v==cha)continue;
h[v]=h[u]+1;
dfs(v,u);
}
}
namespace sub2
{
int h[50068],p[50068],hr[50068];
int getl(int l,int r){
return (h[r]-h[l-1]*p[r-l+1]%mod+mod)%mod;
}
int getr(int i, int j) {
return (hr[i] - hr[j+1] * p[j-i+1]%mod+mod)%mod;
}
bool check(int i,int j){
return (getl(i,j)==getr(i,j));
}
void solve(void)
{
p[0]=1;
for(int i=1;i<=n;i++){
h[i]=(h[i-1]*base+s[i]-'a'+1)%mod;
p[i]=(p[i-1]*base)%mod;
}
for(int i=n;i>=1;i--)
hr[i]=(hr[i+1]*base+s[i]-'a'+1)%mod;
int ans=0;
for(int i=1;i<=n;i++){
int l=0,r=min(n-i,i);
while(l<=r){
int mid=(l+r)/2;
if(check(i-mid+1,i+mid)){
ans=max(ans,mid*2);
l=mid+1;
}
else
r=mid-1;
}
l=0,r=min(i-1,n-i);
while(l<=r){
int mid=(l+r)/2;
if(check(i-mid,i+mid)){
ans=max(ans,mid*2+1);
l=mid+1;
}
else
r=mid-1;
}
}
cout<<ans;
}
}
namespace sub1
{
int ans=1,goc;
int D_odd[maxn],D_even[maxn];
void Calc_D_odd(string S) {
int N=S.size();
S=" "+S;
int L = 1;
int R = 0;
for(int i = 1 ; i <= N ; i++) {
if(i > R) D_odd[i] = 0;
else D_odd[i] = min(R - i, D_odd[L + (R - i)]);
while(i - D_odd[i] - 1 > 0 && i + D_odd[i] + 1 <= N && S[i - D_odd[i] - 1] == S[i + D_odd[i] + 1]) {
D_odd[i]++;
}
if(i + D_odd[i] > R) {
R = i + D_odd[i];
L = i - D_odd[i];
}
}
}
void Calc_D_even(string S) {
int N=S.size();
S=" "+S;
int L = 1;
int R = 0;
for(int i = 1 ; i < N ; i++) {
int j = i + 1;
if(j > R) D_even[i] = 0;
else D_even[i] = min(R - j + 1, D_even[L + (R - j)]);
while(i - D_even[i] > 0 && j + D_even[i] <= N && S[i - D_even[i]] == S[j + D_even[i]]) {
D_even[i]++;
}
if(i + D_even[i] > R) {
R = i + D_even[i];
L = j - D_even[i];
}
}
}
void manacher(string S)
{
Calc_D_even(S);
Calc_D_odd(S);
int N=S.size();
for(int i=1;i<N;i++)
{
ans=max({ans,D_even[i]*2,D_odd[i]*2+1});
}
}
void dfs(int u,int cha,string tmp)
{
tmp+=s[u];
if(a[u].size()==1&&u!=goc)
manacher(tmp);
for(int v:a[u])
{
if(v==cha)continue;
dfs(v,u,tmp);
}
}
void solve(void)
{
for(int i=1;i<=n;i++)
{
goc=i;
dfs(i,-1,"");
}
cout<<ans;
}
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
if(fopen(task".inp","r")){
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);}
cin>>n;
for(int i=1;i<=n;i++)cin>>s[i];
for(int i=1;i<n;i++)
{
int u,v;
cin>>u>>v;
a[u].push_back(v);
a[v].push_back(u);
}
dfs(1,-1);
if(h[n]==n-1)sub2::solve();
else sub1::solve();
cerr <<endl<< "TIME : " << clock() * 0.001 << "s" << endl ;
}
