#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int k;
  if (n % 2 == 0)
    k = n / 2;
  else
    k = ((n - 3) / 2) + 1;
  cout << k << endl;
  for (int i = 0; i < k - 1; i++) cout << 2 << " ";
  if (n % 2 == 0)
    cout << 2;
  else
    cout << 3;
}
