#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;
//	fprintf(g,"%s\n",S);
	for(int i=1;i<nr;i++)
		if(S[i] == S[i-1])
		{
			int j;
			for(j=S[i]+1;!A[j] && j<='z';j++);
			if(j < 'z' + 1)
			{
				P = A[j];
				if(S[A[j]+1] == S[A[j]])
					A[j] ++;
				else
					A[j] = 0;
				swap(i,P);
			}
		}
	for(int i=0;i<nr;i++)
		if(!A[S[i]])
			A[S[i]] = i;
	for(int i=nr-2;S[i] == S[i+1];)
	{
		int j;
		int c = S[i];
		for(j = i-1;S[j] == S[i] || S[j-1] == S[i];j--);
		for(int k=i-1;k>=j;k--)
			swap(k,k+1);
	}
	fprintf(g,"%s",S);
	
	fclose(g);
	fclose(f);
	return 0;
}