#include<bits/stdc++.h>
using namespace std;
int n;
char a[1000005];
int main() {
	scanf("%d",&n);
	for(int i=1; i<=n; i++) {
		scanf("%s",&a[i]);
	}
	int head=1,tail=n,l=0;
	while(head<=tail) {
		if(l==80){
			printf("\n");
			l=0;
		}
		if(a[head]<a[tail]) {
			printf("%c",a[head]);
			head++;
		} else if(a[head]>a[tail]) {
			printf("%c",a[tail]);
			tail--;
		} else {
			int x=head,y=tail;
			while(a[x]==a[y]) {
				x++,y--;
			}
			if(a[x]<a[y]) {
				printf("%c",a[head]);
				head++;
			} else{
				printf("%c",a[tail]);
				tail--;
			}
		}
		l++;
	}
}