#include <bits/stdc++.h>
using namespace std;
int main() {
  int q, l, k, n, m, a, b, c, sum = 0;
  cin >> l >> k;
  a = l * 2;
  b = l * 5;
  c = l * 8;
  sum = ((a / k) + (b / k) + (c / k));
  if (a % k != 0) sum++;
  if (b % k != 0) sum++;
  if (c % k != 0) sum++;
  cout << sum << endl;
  return 0;
}
