#include <bits/stdc++.h>
using namespace std;
const int MAX = 1e6 + 10;
const int OO = 0x3f3f3f3f;
const double EPS = 1e-6;
const long long MOD = 1000000000;
int main() {
  long long n, k;
  cin >> n >> k;
  long long ans = ceil((double)(n * 2) / (double)k);
  ans += ceil((double)(n * 5) / (double)k);
  ans += ceil((double)(n * 8) / (double)k);
  cout << ans << '\n';
  return 0;
}
