#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, k, count = 0;
  cin >> n >> k;
  count = ceil((n * 2) / k);
  long long int count1 = ceil((n * 5) / k);
  long long int count2 = ceil((n * 8) / k);
  if ((count * k) != (n * 2)) count += 1;
  if ((count1 * k) != (n * 5)) count1 += 1;
  if ((count2 * k) != (n * 8)) count2 += 1;
  cout << count + count1 + count2;
}
