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