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