#include <bits/stdc++.h>
using namespace std;
int main() {
  unsigned long long int n, m;
  scanf("%lld", &n);
  scanf("%lld", &m);
  unsigned long long int r = 2 * n;
  unsigned long long int g = 5 * n;
  unsigned long long int b = 8 * n;
  unsigned long long int a, B, c;
  if (r % m == 0) {
    a = r / m;
  } else {
    a = r / m;
    a++;
  }
  if (g % m == 0) {
    B = g / m;
  } else {
    B = g / m;
    B++;
  }
  if (b % m == 0) {
    c = b / m;
  } else {
    c = b / m;
    c++;
  }
  cout << a + B + c << endl;
  return 0;
}
