#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n, k;
  cin >> n >> k;
  int sum = 0;
  sum += 2 * n / k;
  if (2 * n % k != 0) sum++;
  sum += 5 * n / k;
  if (5 * n % k != 0) sum++;
  sum += 8 * n / k;
  if (8 * n % k != 0) sum++;
  cout << sum;
  return 0;
}
