#include <bits/stdc++.h>
using namespace std;
int main() {
  long int n, k, r, g, b, m = 0;
  cin >> n >> k;
  r = n * 2;
  g = n * 5;
  b = n * 8;
  if (r % k == 0)
    m += r / k;
  else
    m += ((r / k) + 1);
  if (g % k == 0)
    m += g / k;
  else
    m += ((g / k) + 1);
  if (b % k == 0)
    m += b / k;
  else
    m += ((b / k) + 1);
  cout << m << endl;
  return 0;
}
