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