#include<stdio.h>
int main(){
	freopen("ciur.in", "r", stdin);   
    freopen("ciur.out", "w", stdout);
	int n;
	scanf("%d" ,&n);
	int i,j,k, prime[1000], v[500000]={0};
	k=1;
	for(i=1; i*2<=n-1; i++)
		if (v[i]==0){
			k++;
			if (k<1000)
				prime[k]=i*2+1;
			for (j=3*i+1; j*2<=n-1; j=j+1+2*i)
			v[j]=1;}
		
	printf("%d\n", k);
	prime[1]=2;
	for (i=1; i<=k; i++)
		printf("%d ", prime[i]);
	
		
	
	
	
	return 0;
}