#include<iostream>
#include<stdio.h>
using namespace std;   
char vo[123],p;    
int v[123];   
int main()    
{   
FILE *f=fopen("ordine.in","r"), *g=fopen("ordine.out","w");
    //char a[100];   
int i;   
char c;   
        
    //for(i=97;i<=122;i++)   
       //{c=i; vo[i]=c;}   
    //fscanf(f,"%s",&a);   
    //n=s89trlen(a);
while(!feof(f))   
		{fscanf(f,"%c",&p);
         v[(int)p]++;cont++;}   
         for(i=97;i<=122;i++)   
               if(v[i]!=0)   
               // fprintf(g,"%d %c\n",v[i],i);   
	do
	{
		if (v[i]!=0)
		{fprintf(g,"%c",i);p=(int)i; i++;}
		
	}while(i!=cont)       
       
       
       
       

  
fclose(f);   
fclose(g);   
  
return 0;   
}