#include <bits/stdc++.h>
int main(void) {
  int n, k, p, w, c, v, z, x, m, o, u, j;
  scanf("%d", &n);
  scanf("%d", &k);
  p = n * 2;
  w = p % k;
  if (w == 0) {
    c = p / k;
  } else {
    c = (p / k) + 1;
  }
  z = n * 5;
  x = z % k;
  if (x == 0) {
    v = z / k;
  } else {
    v = (z / k) + 1;
  }
  m = n * 8;
  o = m % k;
  if (o == 0) {
    u = m / k;
  } else {
    u = (m / k) + 1;
  }
  j = c + v + u;
  printf("%d", j);
  return 0;
}
