#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vll = vector<ll>;
using db = double;
int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, -1, 0, 1};
bool isPunct(char c) {
  string punct = ".,!?";
  for (int i = (0); i < (((int)(punct).size())); ++i) {
    if (c == punct[i]) {
      return true;
    }
  }
  return false;
}
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  cout.setf(ios::fixed), cout.precision(20);
  int n;
  cin >> n;
  if (n % 2 == 0) {
    cout << n / 2 << endl;
  } else {
    n -= 3;
    cout << 1 + n / 2 << endl;
    cout << 3 << " ";
  }
  for (int k = (0); k < (n / 2); ++k) {
    cout << 2 << " ";
  }
  cout << endl;
  return 0;
}
