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