#include <bits/stdc++.h>
using namespace std;
const long long int mod = 1e9 + 7;
bool isprime(int a) {
  for (int i = 2; i <= sqrt((double)a); i++) {
    if (a % i == 0) return false;
  }
  return true;
}
int main() {
  int n;
  cin >> n;
  if (n <= 7)
    cout << 1 << endl << n;
  else {
    cout << 3 << endl << 3 << " ";
    n -= 3;
    for (int i = 2; i <= n; i++) {
      if (isprime(i) && isprime(n - i)) {
        cout << i << " " << n - i;
        return 0;
      }
    }
  }
}
