#include<bits/stdc++.h>
#define int long long
#define str string
#define task "strdel"
#define ii pair<int,int>
#define iii pair<int,ii>
#define iv pair<ii,ii>
#define se second
#define fi first
#define ffi fi.fi
#define sfi se.fi
#define sse se.se
#define fse fi.se
#define lt(i, c, d) for(int i = c; i <= d; ++i)
#define fl(i, c, d) for(int i = d; i >= c; --i)
#define pb push_back
#define emb emplace_back
#define emf emplace_front
#define em emplace
using namespace std;
const int N=5e4+5,lg=20,mod=1e9+3,base=31;
mt19937 rd(chrono::steady_clock::now().time_since_epoch().count());
int Rand(int u,int v){
return u+rd()%(v-u+1);
}
int n,c[N],ans=1,sz[N],fup[N],fd[N],h[N],up[N][lg+5];
string s;
vector<int>a[N];
bool k[N];
void dfs(int u,int cha){
sz[u]=1;
for(int v:a[u]){
if(v==cha||k[v])continue;
dfs(v,u);
sz[u]+=sz[v];
}
}
int fin(int u,int cha,int n){
for(int v:a[u]){
if(v!=cha&&!k[v]&&sz[v]>n/2)return fin(v,u,n);
}
return u;
}
bool ok=false;
vector<int>node;
vector<ii>store[N];
void calc(int u,int cha){
node.emb(u);
store[h[u]].emb(fd[u],u);
for(int j=1;j<=lg;++j)
up[u][j]=up[up[u][j-1]][j-1];
for(int v:a[u]){
if(v==cha||k[v])continue;
up[v][0]=u;
h[v]=h[u]+1;
fd[v]=(fd[u]*base+s[v]-'a'+1)%mod;
fup[v]=(fup[u]+(s[v]-'a'+1)*c[h[u]])%mod;
calc(v,u);
}
}
int lift(int x,int k){
for(int i=lg;i>=0;--i){
if(k>=(1LL<<i)){
k-=(1LL<<i);
x=up[x][i];
}
}
return x;
}
int gethash(int u,int v){
return ((fd[u]-fd[up[v][0]]*c[h[u]-h[v]+1])%mod+mod)%mod;
}
int lca(int u,int v){
if(h[u]<h[v])swap(u,v);
for(int j=lg;j>=0;--j){
if(h[u]-h[v]>=(1<<j))u=up[u][j];
}
if(u==v)return u;
for(int j=lg;j>=0;--j){
if(up[u][j]!=up[v][j]){
u=up[u][j];
v=up[v][j];
}
}
return up[u][0];
}
void giai(int u,int cha,int mid){
fup[u]=s[u]-'a'+1;
fd[u]=s[u]-'a'+1;;
node.clear();
up[u][0]=0;
h[u]=1;
calc(u,cha);
for(int i=1;i<=n;++i){
if(store[i].empty())break;
sort(store[i].begin(),store[i].end());
// cout <<i<<" ";
}
// cout<<'\n';
// cout <<node.size()<<" ";
for(int i:node){
if(ok)break;
int dep=mid-h[i]+1;
// cout <<i<<" "<<dep<<'\n';
if(dep>h[i]||dep<1)continue;
int X=lift(i,dep-1);
if(fd[X]!=fup[X])continue;;
int tmp=gethash(i,X);
int l=lower_bound(store[dep].begin(),store[dep].end(),make_pair(tmp,0LL))-store[dep].begin();
if(l==store[dep].size()||store[dep][l].fi!=tmp)continue;
while(l<store[dep].size()){
if(store[dep][l].fi!=tmp)break;
if(lca(i,store[dep][l].se)==u){
ok=true;
break;
}
++l;
}
}
for(int i=1;i<=n;++i){
if(store[i].empty())break;
// sort(store[i].begin(),store[i].end());
store[i].clear();
}
}
void cen(int u,int mid){
if(ok)return;
// cout <<u<<" "
dfs(u,u);
int g=fin(u,u,sz[u]);
k[g]=true;
giai(g,u,mid);
for(int v:a[g]){
if(k[v])continue;
// if(ok)return;
cen(v,mid);
}
}
void solve(){
cin >> n >>s;
for(int i=1;i<n;++i){
int u,v;
cin >> u >> v;
a[u].emb(v);
a[v].emb(u);
}
s=" "+s;
c[0]=1;
for(int i=1;i<=n;++i)c[i]=(c[i-1]*base)%mod;
// chatle();
int r=1,l=n/2;
while(r<=l){
ok=false;
for(int i=1;i<=n;++i)k[i]=false;
int mid=(r+l)>>1LL;
cen(1,mid*2);
if(ok){
ans=max(ans,mid*2);
r=mid+1;
}
else l=mid-1;
}
r=1,l=n/2;
while(r<=l){
for(int i=1;i<=n;++i)k[i]=false;
ok=false;
int mid=(r+l)>>1LL;
cen(1,mid*2+1);
// cout <<mid<<'\n';
if(ok){
ans=max(ans,mid*2+1);
r=mid+1;
}
else l=mid-1;
}
cout << ans;
}
main()
{
srand(time(0));
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
if(fopen(task".inp","r")){
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
int t=1;
// cin >> t;
while(t--){
solve();
cout<<'\n';
}
}
