#include <bits/stdc++.h>
using namespace std;
int main() {
  long int n, m, r, g, b, r1, g1, b1;
  cin >> m >> n;
  r = m * 2;
  g = m * 5;
  b = m * 8;
  if (r % n == 0)
    r1 = r / n;
  else
    r1 = (r / n) + 1;
  if (g % n == 0)
    g1 = g / n;
  else
    g1 = (g / n) + 1;
  if (b % n == 0)
    b1 = b / n;
  else
    b1 = (b / n) + 1;
  cout << (r1 + b1 + g1) << endl;
}
