#include <bits/stdc++.h>
using namespace std;
int main() {
  long double n, k, r, g, b;
  long long int sum = 0;
  cin >> n >> k;
  r = 2 * n;
  g = 5 * n;
  b = 8 * n;
  sum += ceil(r / k);
  sum += ceil(g / k);
  sum += ceil(b / k);
  cout << sum << endl;
}
