#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int cmpfunc(const void *a, const void*b){
    return(*(char*)a - *(char*)b);
}
int main(){
    int n;
    char boxes[1000];
    scanf("%d", &n);
    scanf("%s",boxes);
    
    qsort(boxes, n,sizeof(char),cmpfunc);
    int left = 0,right = n - 1;
    char result[1000];
    int idx = 0;
    while (left<=right){
        result[idx++]=boxes[right--];
    }
}
result[idx]='\0';
printf("%s\n",result);
return 0;
}