#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  long long red = 2 * n;
  long long green = 5 * n;
  long long blue = 8 * n;
  int res = 0;
  res += (red / k);
  if (red % k != 0) {
    res++;
  }
  res += (green / k);
  if (green % k != 0) {
    res++;
  }
  res += (blue / k);
  if (blue % k != 0) {
    res++;
  }
  cout << res << endl;
  return 0;
}
