#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const long long MAX = 1e6 + 10;
long long a[100005];
int main() {
  long long n, k, m, sum, t, len;
  string s, d;
  while (cin >> n) {
    int flag = 1;
    sum = 0;
    if (n % 2 == 0) {
      cout << n / 2 << endl;
      for (long long i = (1); i <= (n / 2); ++i) cout << "2" << ' ';
      cout << endl;
    } else {
      cout << (n - 3) / 2 + 1 << endl;
      for (long long i = (1); i <= ((n - 3) / 2); ++i) cout << "2" << ' ';
      cout << "3" << endl;
    }
  }
  return 0;
}
