#include<bits/stdc++.h> using namespace std; int a[10002] = {}; int sum; void su(int sum) { int flagi = 1; int flagj = 1; for(int i = 2; i < sum; i++) { int j = sum - i; for(int k = 2; k < i; k++) { if(i % k == 0) { flagi = 0; break; } } for(int k = 2; k < j; k++) { if(j % k == 0) { flagj = 0; break; } } if(flagi == 1 && flagj == 1) { a[i] = i * j; } } } int bj(int a[10002]) { int max = -1; for(int i = 2; i < sum; i++) { if(a[i] > max) { max = a[i]; } } return max; } int main() { cin >> sum; su(sum); cout << bj(a); return 0; }