#include <bits/stdc++.h>
using namespace std;
int main() {
  double n, k, a, b, c;
  unsigned long long int total;
  cin >> n >> k;
  a = ceil((n * 2) / k);
  b = ceil((n * 5) / k);
  c = ceil((n * 8) / k);
  total = a + b + c;
  cout << total << "\n";
  return (0);
}
