#include<fstream.h>
ifstream f("ciur.in");
ofstream g("ciur.out");
char prim[1000005];
long long n,p;

int main()
{f>>n;
 int j,i=1;
 int nr=2;
 int prod=(2*i+1)*(2*i+1);
 int ceva=2*i+1;
 while(prod<n)
	{for(j=(prod-1)/2;j<=n/2;j+=ceva)
		prim[j]=1;
	 i++;
	 while(prim[i]==1) i++;
	 prod=(2*i+1)*(2*i+1);
	 ceva=2*i+1;
	 nr++;
	}
 for(i=i+1;i<n/2;i++)
	if(prim[i]==0) nr++;
 g<<nr<<'\n';
 if(nr<=1000)
	{g<<2;
	 for(i=1;i<n/2;i++)
		if(prim[i]==0) g<<' '<<2*i+1;
	 }
 else {i=n/2;
	   int cnt=1000;
	   while(cnt>0)
		{if(prim[i]==0)
			cnt--;
		 i--;}
	   while(prim[i]==1) i++;
	   g<<2*i+1;
	   i++;
	   for(;cnt<1000;i++)
		 if(prim[i]==0) {g<<' '<<2*i+1;cnt++;}
	  }
 f.close();
 g.close();
 return 0;
}