#include "math.h"
#include "stdio.h"
void main()
{
	char a[10];
	int n,i,j,c;
	scanf("%d\n",&n);
	for (i=0;i<n;i++)
	{
		a[i]=getchar();
	}
	for (i=0;i<n-1;i++)
	{
		c=i;
		for (j=i+1;j<n;j++)
		{
			if (a[j]<a[i]) c=j;
		}
		printf("%c",a[c]);
		a[c]=a[i];
	}
    printf("%c\n",a[n-1]);
}