#include <bits/stdc++.h>
using namespace std;
int r = 2, g = 5, b = 8, n, k;
int h, j, p;
int main() {
  cin >> n >> k;
  h = r * n;
  j = g * n;
  p = b * n;
  h = (h + k - 1) / k;
  j = (j + k - 1) / k;
  p = (p + k - 1) / k;
  cout << p + j + h;
}
