// input code here
```include<stdio.h>
int main()
{
int a[1001],i,n,tong,b=0;
for(i=1;i<=1000;i++)
{
a[i]=0;
 }
 scanf("%d",&n);
for(i=1;i<=n;i++)
{
    scanf("%d",&tong);
    if(a[tong]!=1)
    {
    a[tong]=1;
    b++; 
    }
}
     printf("%d\n",b);
 for(i=1;i<=1000;i++)
 {
     if(a[i]==1)
      printf("%d ",i);
 }
}