#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, w;
  cin >> n >> w;
  long long a[2 * n];
  for (int i = 0; i < 2 * n; i++) {
    cin >> a[i];
  }
  sort(a, a + 2 * n);
  double maxi = a[n], mini = a[0];
  double kam = min(maxi / 2, mini);
  double ans = min((double)w, 3 * kam * n);
  cout << std::fixed << ans << endl;
  return 0;
}
