//#include <bits/stdc++.h> #include <iostream> using namespace std; bool isprime(int n) { for (int i = 2; i < n; i++) { if (n % i == 0) { return false; } } return true; } int main() { //freopen("1519.in", "r", stdin); //freopen("1519.out", "w", stdout); int s, max = 0; cin >> s; for (int i = 2; i <= s / 2; i++) { if (isprime(i) && isprime(s - i)) { if (i * (s - i) > max) { max = i * (s - i); } } } cout << max << endl; return 0; }