#include <bits/stdc++.h>
using namespace std;
int lol(int a, int b) {
  if (a % b == 0)
    return a / b;
  else
    return a / b + 1;
}
int main() {
  long long x, k;
  cin >> x >> k;
  cout << lol(2 * x, k) + lol(5 * x, k) + lol(8 * x, k) << endl;
}
