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