#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 123;
const int M = 1e7 + 123;
const int inf = 1e9 + 1;
const int mod = 1e9 + 7;
const int bl = 300;
int n, cnt;
vector<int> ans;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  while (n >= 2) {
    if (n == 3) {
      ans.push_back(3);
    } else {
      ans.push_back(2);
    }
    n -= 2;
  }
  cout << ans.size() << endl;
  for (int i = 0; i < ans.size(); ++i) {
    cout << ans[i] << ' ';
  }
  return 0;
}
