# include<iostream> using namespace std; bool is_pi(int n) { if(n<=1)return false; for(int i = 2; i <= n/i; i++){ if(n % i == 0)return false; } return true; } int main(){ int s, l[10000], n=0, _max=0; cin>>s; for(int i = 2; i <= s/2; i++)if(is_pi(i)){ l[n]=i; n++; } for(int i = 0; i < n; i++)if(is_pi(s-l[i])&&(s-l[i])*l[i]>_max)_max=(s-l[i])*l[i]; cout<<_max; return 0; }