#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
int main() {
  long long n, k;
  cin >> n >> k;
  long long r = n * 2;
  long long g = n * 5;
  long long b = n * 8;
  long long count = 0;
  if (r % k == 0) {
    count = count + r / k;
  } else {
    count = count + r / k + 1;
  }
  if (b % k == 0) {
    count = count + b / k;
  } else {
    count = count + b / k + 1;
  }
  if (g % k == 0) {
    count = count + g / k;
  } else {
    count = count + g / k + 1;
  }
  cout << count << "\n";
  return 0;
}
