#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  long long n, k;
  cin >> n >> k;
  long long red = n * 2;
  long long green = n * 5;
  long long blue = n * 8;
  long long t(0);
  if (red == k)
    t++;
  else if (red > k and red % k != 0)
    t += (red / k) + 1;
  else if (red > k and red % k == 0)
    t += (red / k);
  else if (red < k)
    t++;
  if (green == k)
    t++;
  else if (green > k and green % k != 0)
    t += (green / k) + 1;
  else if (green > k and green % k == 0)
    t += (green / k);
  else if (green < k)
    t++;
  if (blue == k)
    t++;
  else if (blue > k and blue % k != 0)
    t += (blue / k) + 1;
  else if (blue > k and blue % k == 0)
    t += (blue / k);
  else if (blue < k)
    t++;
  cout << t << endl;
  return (0);
}
