#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  cout << (n / 2) << endl;
  for (int i = 0; i < (n - 2) / 2; i++) cout << 2 << ' ';
  if (n % 2 == 0)
    cout << 2;
  else
    cout << 3;
  return 0;
}
