#include <bits/stdc++.h>
const long double pi = 3.14159265359;
using namespace std;
double mi(double a, double b) {
  if (a > b) return b;
  return a;
}
void Prepere_streams() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
}
template <typename MyType>
void out(MyType MyValue) {
  cout << MyValue << '\n';
}
template <typename MyType>
void out(vector<MyType> Vector) {
  for (int i = 0; i < Vector.size(); ++i) cout << Vector[i] << ' ';
  cout << '\n';
}
double a[200005];
int main() {
  Prepere_streams();
  int n, w;
  cin >> n >> w;
  for (int i = 0; i < 2 * n; ++i) {
    cin >> a[i];
  }
  sort(a, a + 2 * n);
  double x = mi(a[0], a[n] / 2);
  double r = mi(w, 3 * n * x);
  std::cout << std::fixed << std::setprecision(9) << r;
  return 0;
}
