#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  cout << n / 2 << '\n';
  if (n % 2) {
    cout << "3 ";
    n -= 3;
  }
  while (n) {
    cout << "2 ";
    n -= 2;
  }
}
