#include <bits/stdc++.h>
using namespace std;
const long long N = 1e7;
const long long mod = 1e9 + 7;
long long prime[N + 1];
vector<long long> pr;
void sieve() {
  prime[0] = 0;
  prime[1] = 1;
  for (long long i = 2; i <= N; i++) {
    if (prime[i] == 0) {
      for (long long j = i * i; j <= N; j += i) {
        prime[j] = 1;
      }
    }
  }
}
int32_t main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(NULL);
  sieve();
  long long n;
  cin >> n;
  vector<long long> ans;
  if (n % 2) ans.push_back(3), n -= 3;
  if (n == 2) ans.push_back(2), n -= 2;
  if (n > 0) {
    long long x = n;
    while (x > 0) {
      long long z = sqrt(x), flag = 0;
      for (long long i = 2; i <= z; i++) {
        if (x % i == 0) {
          flag = 1;
          break;
        }
      }
      if ((flag == 0) && (prime[n - x] == 0)) {
        ans.push_back(x);
        ans.push_back(n - x);
        break;
      }
      x--;
    }
  }
  cout << ans.size() << "\n";
  for (auto i : ans) cout << i << " ";
  return 0;
}
