#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int red = n * 2 / k;
  int green = n * 5 / k;
  int blue = n * 8 / k;
  if (red < n * 2.0 / k) {
    red = red + 1;
  }
  if (green < n * 5.0 / k) {
    green = green + 1;
  }
  if (blue < n * 8.0 / k) {
    blue += 1;
  }
  cout << red + green + blue << endl;
  return 0;
}
