#include <bits/stdc++.h>   using namespace std;   const long long int mod = 1e9 + 7;   bool isprime(int a) {     for (int i = 2; i <= sqrt((double)a); i++) {       if (a % i == 0) return false;     }     return true;   }   int main() {     int n;     cin >> n;     if (n <= 7)       cout << 1 << endl << n;     else {       cout << 3 << endl << 3 <<    ;       n -= 3;       for (int i = 2; i <= n; i++) {         if (isprime(i) && isprime(n - i)) {           cout << i <<     << n - i;           return 0;         }       }     }   }   