#include <bits/stdc++.h>
using namespace std;
int main() {
  std::ios_base::sync_with_stdio(0);
  long long n, k;
  cin >> n >> k;
  long long a = (2 * n), b = (5 * n), c = (8 * n);
  a = (a + k - 1) / k;
  b = (b + k - 1) / k;
  c = (c + k - 1) / k;
  cout << (a + b + c) << "\n";
}
