#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
const int inf = 1e9 + 9;
const long long INF = 1e18 + 3;
const long double eps = 1e-9;
const long double PI = acos(-1.0);
const long double E = 2.71828182845904523536;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n, k;
  cin >> n >> k;
  int ans;
  ans = (2 * n + k - 1) / k;
  ans += (5 * n + k - 1) / k;
  ans += (8 * n + k - 1) / k;
  cout << ans << endl;
  return 0;
}
