#include <bits/stdc++.h>
using namespace std;
const long long int INF = LLONG_MAX;
vector<long long int> v1, v2;
string s1, s2, s3;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int a, b, c, d, e, f, i, j, k, cnt1 = 0, cnt2 = 0, sum1 = 0,
                                           sum2 = 0, chk1 = 0, chk2 = 0, T;
  cin >> a >> b;
  long long int lagbe = 2 * a;
  long long int ans = (lagbe / b);
  if (lagbe % b) ans++;
  lagbe = 5 * a;
  ans += (lagbe / b);
  if (lagbe % b) ans++;
  lagbe = 8 * a;
  ans += (lagbe / b);
  if (lagbe % b) ans++;
  cout << ans << endl;
  return 0;
}
