#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int rd = n * 2;
  int gr = n * 5;
  int bl = n * 8;
  int a = 0;
  if (rd % k != 0) {
    a += rd / k + 1;
  } else if (rd % k == 0) {
    a += rd / k;
  }
  if (gr % k != 0) {
    a += gr / k + 1;
  } else if (gr % k == 0) {
    a += gr / k;
  }
  if (bl % k != 0) {
    a += bl / k + 1;
  } else if (bl % k == 0) {
    a += bl / k;
  }
  cout << a;
  return 0;
}
