#include <bits/stdc++.h>
using namespace std;
int main() {
  cin.tie(0);
  cout.tie(0);
  ios_base::sync_with_stdio(0);
  ;
  int a, c, sum = 0;
  cin >> a >> c;
  cout << ((2 * a + c - 1) / c + (5 * a + c - 1) / c + (8 * a + c - 1) / c)
       << endl;
}
