#include <fstream.h>
long long n,i,j,m,w=1;
char prim[2000030];
int main()
{
ifstream f("ciur.in");
ofstream g("ciur.out");
f>>n;
for (i=2;i<=n;i++)
     prim[i]=1;
for (i=2;i<=n;i++)
	if (prim[i]==1)
	{
	 m++;
	 for (j=2*i;j<=n;j=j+i)
	      prim[j]=0;
	}
g<<m<<'\n';
if (n>1002)
    {while (w<=1000)
     i=n;
       if (prim[i]==1)
	 g<<i<<" ";
     i--;w++;}
else {for (i=2;i<=n;i++)
	 if (prim[i]==1) g<<i<<" ";}

f.close();
g.close();
return 0;
}