#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, k;
  cin >> n >> k;
  int r = 2 * n;
  int g = 5 * n;
  int b = 8 * n;
  r = ceil((double)r / k);
  g = ceil((double)g / k);
  b = ceil((double)b / k);
  cout << r + g + b;
  return 0;
}
