/* I LOVE CATTUONG */
//
#include <bits/stdc++.h>
#define CatTuong ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
using namespace std;
#define int long long
//suff:abc pre:cba
// palin suff*pow[h-x]-pre
const int N=5e4+5;
const int MOD=1e9+7;
const int base=32;
int sz[N],heavy[N],mx_h,powB[N],n,ans;
char a[N];
bool is_cen[N];
unordered_map<int,bool>mp[N];
vector<int>g[N];
int add(int x,int y){return (x+y)%MOD;};
int mul(int x,int y){return (x*y)%MOD;};
int sub(int x,int y){return ((x-y)+MOD)%MOD;}
void DFS(int u,int p){
sz[u]=1;
int mx_son_sz=0;
for(auto v:g[u]){
if(v!=p && !is_cen[v]){
DFS(v,u);
sz[u]+=sz[v];
if(sz[v]>mx_son_sz){
mx_son_sz=sz[v];
heavy[u]=v;
}
}
}
}
int find_cen(int u,int p,int tree_sz){
for(auto v:g[u]){
if(v!=p && !is_cen[v] && sz[v]>tree_sz/2){
return find_cen(v,u,tree_sz);
}
}
return u;
}
bool get(int u,int p,int cur_h,int cur_pre_hash,int cur_suff_hash,int &H){
if(cur_h>mx_h)
return 0;
H=max(H,cur_h);
int preH=add(mul(cur_pre_hash,base),a[u]);
int suffH=add(mul(a[u],powB[cur_h-1]),cur_suff_hash);
int tmp=sub(mul(suffH,powB[H-cur_h]),preH);
if(suffH==preH && cur_h==mx_h)
return 1;
if(mp[mx_h-cur_h].find(tmp)!=mp[mx_h-cur_h].end())
return 1;
for(auto v:g[u]){
if(v!=p && !is_cen[v])
if(get(v,u,cur_h+1,preH,suffH,H))
return 1;
}
return 0;
}
void update(int u,int p,int cur_h,int cur_pre_hash,int cur_suff_hash,int &H){
if(cur_h>H)
return;
H=max(H,cur_h);
int preH=add(mul(cur_pre_hash,base),a[u]);
int suffH=add(mul(a[u],powB[cur_h-1]),cur_suff_hash);
int tmp=sub(mul(suffH,powB[H-cur_h]),preH);
mp[cur_h][tmp]=1;
for(auto v:g[u]){
if(v!=p && !is_cen[v])
update(v,u,cur_h+1,preH,suffH,H);
}
}
bool build_cen(int u){
DFS(u,-1);
int cen=find_cen(u,-1,sz[u]);
is_cen[cen]=true;
int H=0;
for(auto v:g[cen]){
if(v!=cen && !is_cen[v]){
if(get(v,cen,2,a[cen],a[cen],H))
return 1;
update(v,cen,1,0,0,H);
}
}
for(int i=0;i<=H;++i){
mp[i].clear();
}
for(auto v:g[cen]){
if(!is_cen[v]){
return build_cen(v);
}
}
return 0;
}
int check(int x){
for(int i=1;i<=n;++i){
mp[i].clear();
is_cen[i]=false;
}
mx_h=x;
return build_cen(1);
}
signed main(){
#define Tuong "Lampice"
// freopen(Tuong".inp","r",stdin);
// freopen(Tuong".out","w",stdout);
CatTuong
cin>>n;
for(int i=1;i<=n;++i)
cin>>a[i];
for(int i=1;i<n;++i){
int u,v;cin>>u>>v;
g[u].push_back(v);
g[v].push_back(u);
}
powB[0]=1;
for(int i=1;i<=n;++i){
powB[i]=mul(powB[i-1],base);
}
int lo=0,hi=n;
while(hi>=lo){
int mid=(hi+lo)>>1;
if(2*mid<=n){
if(check(2*mid)){
ans=2*mid;
lo=mid+1;
}
else
hi=mid-1;
}
else
hi=mid-1;
}
lo=0,hi=n;
while(hi>=lo){
int mid=(hi+lo)>>1;
if(2*mid+1<=n){
if(check(2*mid+1)){
ans=max(ans,2*mid+1);
lo=mid+1;
}
else
hi=mid-1;
}
else
hi=mid-1;
}
cout<<ans;
return 0;
}
