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