#include <bits/stdc++.h>
using namespace std;
bool check(int p) {
  if (p == 2) return 1;
  if (p % 2 == 0) return 0;
  for (long long int i = 3; i * i <= p; i += 2) {
    if (p % i == 0) return 0;
  }
  if (p > 2) return 1;
  return 0;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t = 1;
  while (t--) {
    int n;
    cin >> n;
    if (check(n)) {
      cout << "1" << '\n';
      cout << n << '\n';
      continue;
    }
    if (check(n - 2)) {
      cout << "2" << '\n';
      cout << "2" << ' ' << n - 2 << '\n';
      continue;
    }
    cout << "3" << '\n';
    int a;
    for (int i = n; i > 3; i--) {
      if (check(i)) {
        a = i;
        n -= a;
        break;
      }
    }
    cout << a << ' ';
    for (int i = 2; i <= n; i++) {
      if (check(i) && check(n - i)) {
        cout << i << ' ' << n - i << '\n';
        break;
      }
    }
  }
  return 0;
}
