#include <bits/stdc++.h>
int main() {
  long long int n, k, r, g, b;
  scanf("%lld%lld", &n, &k);
  r = n * 2;
  r = r % k == 0 ? r / k : (r / k) + 1;
  g = n * 5;
  g = g % k == 0 ? g / k : (g / k) + 1;
  b = n * 8;
  b = b % k == 0 ? b / k : (b / k) + 1;
  k = r + g + b;
  printf("%d", k);
  return 0;
}
