#include <bits/stdc++.h>
int main() {
  int n, k;
  scanf("%d %d", &n, &k);
  int r = n * 2;
  int g = n * 5;
  int b = n * 8;
  r = (r / k) + (r % k > 0);
  g = (g / k) + (g % k > 0);
  b = (b / k) + (b % k > 0);
  int sum = r + g + b;
  printf("%d", sum);
  return 0;
}
