#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, i, j, k, w;
  cin >> n >> w;
  long long int A[2 * n];
  for (i = 0; i < 2 * n; i++) cin >> A[i];
  sort(A, A + 2 * n);
  cout << fixed << setprecision(7);
  double num = A[n] / 2.0;
  double num1 = A[0];
  if (num1 < num) num = num1;
  if (w < (3 * n * num))
    cout << w << endl;
  else
    cout << (3 * n * num) << endl;
  return 0;
}
