#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 << " ";
  }
  if (n % 2 != 0) {
    cout << n / 2 << endl;
    for (int j = 0; j < n / 2 - 1; j++) cout << 2 << " ";
    cout << 3;
  }
}
