#include <bits/stdc++.h>
using namespace std;
vector<long long> v1;
vector<long long>::iterator upper, lower, it;
vector<vector<long long>> vect(200005);
void solve() {
  long long n = 0, m = 0, i = 0, j = 0, l = 0, r = 0, x = 0, y = 0, q = 0,
            z = 0, len = 0, k = 0;
  long long a[200005] = {0}, b[200005] = {0}, c[200005] = {0}, p[200005] = {0},
            d[200005] = {0};
  char s[300005], t[300005];
  cin >> n >> k;
  x = 2 * n;
  y = 5 * n;
  z = 8 * n;
  long long ans = 0;
  if (x % k == 0) {
    ans += (x / k);
  } else {
    ans += (x / k) + 1;
  }
  if (y % k == 0) {
    ans += (y / k);
  } else {
    ans += (y / k) + 1;
  }
  if (z % k == 0) {
    ans += (z / k);
  } else {
    ans += (z / k) + 1;
  }
  cout << ans;
}
bool imp = false;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t = 1;
  if (imp) cin >> t;
  while (t--) solve();
  return 0;
}
