#include<cstdio>
using namespace std;
char v[2000001];
int main()
{unsigned long n,i,j,m=0;

freopen("ciur.in","r",stdin);
freopen("ciur.out","w",stdout);
scanf(" %l",&n);

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

printf("%l\n",m);
j=1;
for(i=n;j<=m&&j<=10000;--i)if(!v[i]){++j;}
++i;
for(;i<=n;++i)if(!v[i])printf("%l",i);


return 0;
}