#include <bits/stdc++.h>
#define ll long long
#define mid (l+r>>1)
#define P 1007
using namespace std;
const int N=500005;
int n,m,k,s,t,a[N<<1];
unsigned long long H[N<<1],qpow[N<<1];
char c;
unsigned ll calc(int l,int r){
	return H[r]-H[l-1]*qpow[r-l+1];
}
int main(){
	cin>>n;
	for (int i=1;i<=n;++i) {
		cin>>c;a[i]=c;a[n+n-i+1]=c;
	}
	qpow[0]=1;
	for (int i=1;i<=(n<<1);++i){	
		H[i]=H[i-1]*P+a[i];
		qpow[i]=qpow[i-1]*P;
	}
	s=1,t=n;k=0;
	while (s<=t){
		int l=1,r=(t-s+1)/2;
		while (l<=r){
			if (calc(s,s+mid-1)==calc(n+n-t+1,n+n-(t-mid+1)+1))
				l=mid+1;
			else r=mid-1;
		}
		if (a[s+l-1]<a[t-l+1]) cout<<(char)(a[s++]);
		else cout<<(char)(a[t--]);
		if (++k%80==0) cout<<"\n";
	} 
}