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