#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int red = 2 * n;
  int green = 5 * n;
  int blue = 8 * n;
  int total = 0;
  if (red % k == 0) {
    total += red / k;
  } else {
    total += red / k + 1;
  }
  if (green % k == 0) {
    total += green / k;
  } else {
    total += green / k + 1;
  }
  if (blue % k == 0) {
    total += blue / k;
  } else {
    total += blue / k + 1;
  }
  cout << total;
  return 0;
}
