#include <bits/stdc++.h>
using namespace std;
int cheack(string s, int l, int n) {
  int arra[10] = {0};
  char m = n + '0';
  for (int k = 0; k < l; k++) {
    if (s[k] <= m) {
      int g = s[k] - '0';
      arra[g] = 1;
    }
  }
  for (int p = 0; p <= n; p++) {
    if (arra[p] != 1) {
      return 2;
    }
  }
  return 1;
}
int main() {
  double n, weight, value = 0, a = 0, b = 0, t, x, y, w, l = 0, trump, cost = 0;
  string s;
  bool flag = true;
  char c;
  cin >> a >> b;
  int red = ceil((a * 2) / b * 1.00);
  int blue = ceil((a * 5) / b * 1.00);
  int green = ceil((a * 8) / b * 1.00);
  cout << red + green + blue << endl;
}
