#include<stdio.h>
char v[26],x,w[10000];
int n,i,k;

int main(){
FILE *f=fopen("ordine.in","r");
while(!feof(f)){
fscanf(f,"%c",&x);
if(feof(f))break;
v[x-96]++;n++;
}

fclose(f);

for(i=1;i<=26;i++){
k=1;

  while(v[i]!=0){
    if(w[k-1]!=i&&w[k]==0){
    v[i]--;
    w[k]=i;
    }
  k++;
  }
}
FILE *g=fopen("ordine.out","w");
for(i=1;i<=n;i++){
fprintf(g,"%c",w[i]+96);
}

fclose(g);
return 0;
}