#include <bits/stdc++.h>
using namespace std;
clock_t time_p = clock();
void timer() {
  time_p = clock() - time_p;
  cerr << "Execution Time: " << (double)(time_p) / CLOCKS_PER_SEC << "\n";
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n, k, r = 2, g = 5, b = 8, cnt = 0, tot = 0;
  cin >> n >> k;
  r *= n;
  g *= n;
  b *= n;
  if (r % k)
    cnt += (r / k + 1);
  else
    cnt += r / k;
  if (g % k)
    cnt += (g / k + 1);
  else
    cnt += g / k;
  if (b % k)
    cnt += (b / k + 1);
  else
    cnt += b / k;
  cout << cnt;
  timer();
  return 0;
}
