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

int v[1001],nec[1001],i,n,j,nr;
char obt[50001];

int main ()
{
    freopen ("economie.in","r",stdin);
    freopen ("economie.out","w",stdout);
    
    scanf ("%d",&n);
    for (i=1;i<=n;i++){
        scanf ("%d",&v[i]);
        obt[v[i]]=2;
        }
    sort (v+1,v+n+1);
    
    for (i=1;i<=v[n];i++)
        if (obt[i]==2){
                       nec[++nr]=i;
                       obt[i]=1;
                       for (j=v[1];j<=v[n];j++)
                           if (obt[j]==1){
                                          if (j+nec[nr]>v[n]) break;
                                          obt[j+nec[nr]]=1;
                                          }
                       }
                       
    printf ("%d\n",nr);
    for (i=1;i<=nr;i++) printf ("%d\n",nec[i]);
    
    return 0;
}