#include <bits/stdc++.h>
using namespace std;
vector<int> p;
bool first[5000] = {0};
void gen() {
  p.push_back(0);
  for (int i = 2; i <= 500; i++) {
    if (!first[i]) {
      p.push_back(i);
      for (int j = 2 * i; j <= 500; j += i) {
        first[j] = 1;
      }
    }
  }
}
bool isprime(int x) {
  int sz = sqrt(x) + 1;
  for (int i = 2; i <= sz; i++) {
    if (x % i == 0) return 0;
  }
  return 1;
}
int main() {
  gen();
  int n;
  cin >> n;
  if (n <= 500) {
    vector<int> ans;
    for (int i = 0; i < p.size(); i++) {
      if (p[i] > n) break;
      for (int j = 0; j <= i; j++) {
        for (int k = 0; k <= j; k++) {
          if (p[i] + p[j] + p[k] == n) {
            if (p[i]) ans.push_back(p[i]);
            if (j) ans.push_back(p[j]);
            if (k) ans.push_back(p[k]);
            cout << ans.size() << "\n";
            for (auto x : ans) {
              cout << x << " ";
            }
            return 0;
          }
        }
      }
    }
  } else {
    vector<int> ans;
    for (int i = n; i >= n - 500; i--) {
      if (isprime(i)) {
        ans.push_back(i);
        n -= i;
        break;
      }
    }
    for (int i = 0; i < p.size(); i++) {
      if (p[i] > n) break;
      for (int j = 0; j <= i; j++) {
        if (p[i] + p[j] == n) {
          if (p[i]) ans.push_back(p[i]);
          if (p[j]) ans.push_back(p[j]);
          cout << ans.size() << "\n";
          for (auto x : ans) {
            cout << x << " ";
          }
          return 0;
        }
      }
    }
  }
  return 0;
}
