#include <bits/stdc++.h>
using namespace std;
const int N = 1000000;
vector<int> v;
int a[N], ans;
int main() {
  int n, k;
  cin >> n >> k;
  ans += (2 * n + k - 1) / k;
  ans += (5 * n + k - 1) / k;
  ans += (8 * n + k - 1) / k;
  cout << ans;
  return 0;
}
