#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 sushu(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,num=0,n1=2,n2,max=0; int arr[20001]={0}; cin>>num; while(n1<=num/2) { n2=num-n1; if(sushu(n2)&&sushu(n1)) { if(max<n1*n2) max=n1*n2; } n1++; } cout<<max<<endl; return 0; }