#include<fstream.h>
#define dim 2000001
#define dim2 1003
char prim[dim];
unsigned long cont,n,a[dim2],ok;
ifstream f("ciur.in");
ofstream g("ciur.out");
int main()
{unsigned long i,j;
f>>n;
f.close();

for(i=2;i<=n;i++)
 if(!prim[i])
   {cont++;
    for(j=i+i;j<=n;j+=i)
     prim[j]=1;
   }

g<<cont<<'\n';

cont=0;ok=1;
for(i=n;(i>=2)&&(ok);i--)
 {if(!prim[i])
   {a[++cont]=i;
    if(cont==1000) ok=0;
   }
 }

for(i=cont;i>=1;i--) g<<a[i]<<" ";
g<<'\n';
g.close();
return 0;
}