#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, k;
  cin >> n >> k;
  long long int a, b, c;
  a = 2 * n;
  b = 5 * n;
  c = 8 * n;
  a = (a + k - 1) / k;
  b = (b + k - 1) / k;
  c = (c + k - 1) / k;
  cout << a + b + c;
}
