#include <bits/stdc++.h>
using namespace std;
const long long N = 100005, INF = 1e18;
void solve() {
  long long n, ans = 0, max = 0;
  cin >> n;
  ans = n / 2;
  cout << ans << '\n';
  for (long long i = (long long)0; i < ans - 1; i++) {
    cout << "2 ";
  }
  if (n % 2 == 0)
    cout << 2 << '\n';
  else
    cout << 3 << '\n';
}
int32_t main() {
  std::ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  long long t = 1;
  while (t--) solve();
}
