#include <bits/stdc++.h>
using namespace std;
int main() {
  int friends, sheets;
  scanf("%d %d", &friends, &sheets);
  int red = friends * 2;
  int green = friends * 5;
  int blue = friends * 8;
  int result = 0;
  result += ceil((double)red / sheets) + ceil((double)green / sheets) +
            ceil((double)blue / sheets);
  printf("%d\n", (int)result);
  return 0;
}
