#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 ";
    return 0;
  } else {
    cout << (n / 2) << endl;
    for (int i = 0; i < (n / 2) - 1; i++) cout << "2 ";
    cout << "3";
    return 0;
  }
}
