#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  while (cin >> n >> k) {
    int sol = 0;
    sol += (n * 2) / k;
    sol += (n * 5) / k;
    sol += (n * 8) / k;
    if ((n * 2) % k != 0) ++sol;
    if ((n * 5) % k != 0) ++sol;
    if ((n * 8) % k != 0) ++sol;
    cout << sol << '\n';
  }
  return 0;
}
