#include<stdio.h>
#include<algorithm>
#include<string.h>
using namespace std;

char S[1000100];
int A[301];
int nr;
int P;

int swap(int a,int b)
{
	int c = S[a];
	S[a] = S[b];
	S[b] = c;
}

int main()
{
	FILE *f = fopen("ordine.in","r");
	FILE *g = fopen("ordine.out","w");
	
	fscanf(f,"%s",&S);
	nr = strlen(S);
	sort(S,S+nr);
	for(int i=0;i<nr;i++)
		if(!A[S[i]])
			A[S[i]] = i;
	for(int i=1;S[i];i++)
		if(S[i] == S[i-1])
		{
			int j;
			for(j=S[i]+1;!A[j];j++);
			P = A[j];
			if(S[A[j]+1] == S[A[j]])
				A[j] ++;
			else
				A[j] = 0;
			swap(i,P);
		}
	fprintf(g,"%s",S);
	
	fclose(g);
	fclose(f);
	return 0;
}