#include <bits/stdc++.h>
using namespace std;
long long r, g, k, n, i, j, a, b, c, e, d, t;
string s;
int main() {
  cin >> n >> k;
  b = n * 8;
  r = n * 2;
  g = n * 5;
  if (r % k == 0)
    e = e + r / k;
  else
    e = e + r / k + 1;
  if (g % k == 0)
    e = e + g / k;
  else
    e = e + g / k + 1;
  if (b % k == 0)
    e = e + b / k;
  else
    e = e + b / k + 1;
  cout << e << " ";
}
