#include <bits/stdc++.h>
using ll = long long;
int main() {
  ll n, k;
  while (std::cin >> n >> k) {
    ll res(0);
    res += (2 * n + k - 1) / k;
    res += (5 * n + k - 1) / k;
    res += (8 * n + k - 1) / k;
    std::cout << res << std::endl;
  }
  return 0;
}
