#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int needRed = 2 * n;
  int needGreen = 5 * n;
  int needBlue = 8 * n;
  int aka1 = needRed / k + (needRed % k != 0);
  int aka2 = needGreen / k + (needGreen % k != 0);
  int aka3 = needBlue / k + (needBlue % k != 0);
  cout << aka1 + aka2 + aka3 << '\n';
  return 0;
}
