#include <bits/stdc++.h>
using namespace std;
long long fact(long long n) {
  long long ans = 1;
  for (long long i = 2; i <= n; i++) {
    ans = ans * i;
  }
  return ans;
}
long long ncr(long long n, long long r) {
  return fact(n) / (fact(r) * fact(n - r));
}
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  srand(time(NULL));
  long long n;
  cin >> n;
  if (n % 2 == 0) {
    cout << n / 2 << "\n";
    for (long long i = 1; i <= n / 2; i++) {
      cout << 2 << " ";
    }
  } else {
    cout << (n - 3) / 2 + 1 << "\n";
    for (long long i = 1; i <= (n - 3) / 2; i++) {
      cout << 2 << " ";
    }
    cout << 3;
  }
  return 0;
}
