# include<iostream> # include<cstring> using namespace std; bool zhi(int n){ for (int i=2;i<=n/2;i++){ if (n%i==0) return false; } return true; } int main(){ int s,i,u,max=0; cin>>s; for (i=2;i<=s/2;i++){ u=s-i; if (zhi(i) && zhi(u)){ if (max<i*u) max=i*u; } } cout<<max; return 0; }