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