#include <bits/stdc++.h>
int main() {
  int n, m;
  int r = 0, a = 0, v = 0;
  double es = 0.0;
  scanf("%d%d", &n, &m);
  r = 2 * n;
  v = 5 * n;
  a = 8 * n;
  es = (double)r / m;
  r = r / m;
  if (es - r != 0.00) {
    r++;
  }
  es = (double)v / m;
  v = v / m;
  if (es - v != 0.00) {
    v++;
  }
  es = (double)a / m;
  a = a / m;
  if (es - a != 0.00) {
    a++;
  }
  printf("%d", a + v + r);
  return 0;
}
