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