#include<stdio.h>
int a[50001],s[50001],n,m,x,i,j;
int main()
{freopen("economie.in","r",stdin);
 freopen("economie.out","w",stdout);
 scanf("%d",&n);
 for(i=1;i<=n;i++)
 {scanf("%d",&x);
  if(a[x]) continue;
  a[x]=1;
  for(i=1;i<=50000-x;i++)  if(a[i]) a[i+x]=1;
  s[++m]=x;}
 printf("%d\n",m);
 for(i=1;i<=m;i++)
  printf("%d\n",s[i]);
 fclose(stdout);
 return 0;}