#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n, w, i;
  cin >> n >> w;
  int arr[2 * n];
  for (i = 0; i < 2 * n; i++) cin >> arr[i];
  sort(arr, arr + 2 * n);
  long double minn = min((long double)arr[0], (long double)arr[n] / 2);
  minn = min(minn, (long double)w / (3 * n));
  minn = minn * 3 * n;
  printf("%.9lf\n", (double)minn);
  return 0;
}
