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