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