#include<stdio.h>
#define gata fcloseall();return 0;
#define citire FILE *f,*g;f=fopen("ciur.in","r");g=fopen("ciur.out","w");fscanf(f,"%ld",&n);
#define eratostene for(i=2;i<=n;i++)if(!ciur[i]){sol++;for(j=2*i;j<=n;j=j+i)ciur[j]=1;}fprintf(g,"%ld\n",sol);
#define afis1 if(sol>1000){j=1000;for(i=n;j;i--)if(!ciur[i]){prim[j]=i;j--;}for(i=1;i<=1000;i++)fprintf(g,"%ld ",prim[i]);gata}
#define afis2 for(i=2;sol;i++)if(!ciur[i]){fprintf(g,"%ld ",i);sol--;}
char ciur[2000002];
long int n,i,sol,j,prim[1002];
int main()
{       citire
	eratostene
	afis1
	afis2
	gata
}