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