#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
const int N = 2e3 + 5, M = 1e4 + 5, OO = 0x3f3f3f3f;
int n, m;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  cout << n / 2 << endl;
  if (n % 2 == 0) {
    m = n / 2;
    while (m--) cout << 2 << " ";
  } else {
    m = n / 2 - 1;
    while (m--) cout << 2 << " ";
    cout << 3;
  }
  return 0;
}
