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