#include <bits/stdc++.h>
using namespace std;
long long f(long long x, long long y) { return (x + y - 1) / y; }
int main() {
  long long n, k;
  cin >> n >> k;
  long long x = 2 * n, y = 5 * n, z = 8 * n;
  cout << f(x, k) + f(y, k) + f(z, k) << endl;
}
