#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int redNoteBook = ceil(2 * n * 1.0 / k);
  int greenNoteBook = ceil(5 * n * 1.0 / k);
  int blueNoteBook = ceil(8 * n * 1.0 / k);
  cout << redNoteBook + greenNoteBook + blueNoteBook;
}
