#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; bool su(int n){ int j; if(n<=1){ return false; } for(j=2;j<=sqrt(n);j++){ if(n%j==0){ return false; } } return true; } int main(){ int i=0,j,s=0,n1=2,n2,max=0; int arr[20001]={0}; cin>>s; while(n1<=s/2){ n2=s-n1; if(su(n2)&&su(n1)){ if(max<n1*n2){ max=n1*n2; } } n1++; } cout<<max<<endl; return 0; }