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