#include<bits/stdc++.h> using namespace std; int s; bool sum (int x){ if(x<2)return false; else{ for(int j=2;j<=sqrt(s);j++){ if(x%j==0)return false; } }return true; } int main() { int a[10001]={0},b[10001]={0},max=0,c[10001]; cin>>s; for(int i=2;i<=s/2;i++){ a[i]=i; b[i]=s-i; if((sum(a[i])&&sum(b[i]))){ if(max<a[i]*b[i]){ max=a[i]*b[i]; } } }cout<<max<<" "; return 0; }