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