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