#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 << " ";
  } else {
    if (n == 3) {
      cout << 1 << endl;
      cout << 3 << endl;
    } else {
      n -= 3;
      cout << n / 2 + 1 << endl;
      for (i = 0; i < n / 2; i++) cout << 2 << " ";
      cout << 3 << endl;
    }
  }
  return 0;
}
