#include <bits/stdc++.h>
using namespace std;
const int maxx = 1e5 + 5;
int n, m, T;
int a[4];
int main() {
  int i, j, k;
  while (scanf("%d %d", &n, &k) == 2) {
    printf("%d\n", (int)ceil(2 * n * 1.0 / k) + (int)ceil(5 * n * 1.0 / k) +
                       (int)ceil(8 * n * 1.0 / k));
  }
  return 0;
}
