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