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