#include <stdio.h>

#include "genlib.h"
#include "simpio.h"
#include "string.h"

void cluster(char s[]);

main()
{
	string s;
	s=GetLine();
	cluster(s);
	printf("%s\n",s);
}

void cluster(char s[])
{
	int i,n1,count_a=0;
	n1=strlen(s);
	for(i=0;i<n1;i++)
		if(s[i]=='a')
			count_a=count_a+1;
	for(i=0;i<count_a;i++)
		s[i]='a';
	for(i=count_a;i<n1;i++)
		s[i]='b';
}