#include <bits/stdc++.h>
using namespace std;
int a[200001];
int main() {
  int n, w;
  cin >> n >> w;
  for (int i = 0; i < 2 * n; i++) {
    cin >> a[i];
  }
  sort(a, a + 2 * n);
  double x = min((double)a[0], (double)a[n] / 2);
  double ans = min((double)w, (double)3 * n * x);
  cout.precision(10);
  cout << fixed;
  cout << ans << endl;
  return 0;
}
