tost.cpp

#include <iostream>

using namespace std;

int main() {
  int k, n;
  cin >> n >> k;
  int t = n * 2 / k;
  if (n*2 % k > 0) t++;
  t *= 2;
  if (t<4 && t!=0) t = 4;
  cout << t << endl;
  return 0;
}