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