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