#include <bits/stdc++.h>
using namespace std;
int main() {
  double n, k;
  long long r = 0, g = 0, b = 0;
  cin >> n >> k;
  r = n * 2;
  g = n * 5;
  b = n * 8;
  long long r2 = ceil(r / k);
  long long g2 = ceil(g / k);
  long long b2 = ceil(b / k);
  cout << r2 + g2 + b2 << endl;
  return 0;
}
