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