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