#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  int n, k;
  cin >> n >> k;
  int r = 2 * n;
  int g = 5 * n;
  int b = 8 * n;
  int ans = ceil((double)r / k) + ceil((double)g / k) + ceil((double)b / k);
  cout << ans;
  return 0;
}
