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