#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, w;
  cin >> n >> w;
  long long int arr[2 * n];
  int i;
  for (i = 0; i < 2 * n; i++) cin >> arr[i];
  sort(arr, arr + 2 * n);
  long double ans = min((long double)arr[0] * 1.0, (long double)arr[n] / (2.0));
  ans = min(ans, (long double)w / (3.0 * n));
  cout.precision(7);
  cout << 3.0 * n * ans << endl;
  return 0;
}
