#include <bits/stdc++.h>
using namespace std;
int main() {
  int a[3] = {2, 5, 8};
  long long n, k, ans = 0;
  cin >> n >> k;
  for (int i = 0; i < 3; i++) ans += (n * a[i]) / k + ((n * a[i]) % k != 0);
  cout << ans << endl;
}
