#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie();
  long n;
  double w;
  cin >> n >> w;
  vector<double> cups(2 * n);
  for (long p = 0; p < 2 * n; p++) {
    cin >> cups[p];
  }
  sort(cups.begin(), cups.end());
  double girl = cups[0];
  double boy = cups[n];
  double ans = (2 * girl < boy) ? (3 * n * girl) : (1.5 * n * boy);
  if (ans > w) {
    ans = w;
  }
  cout << fixed;
  cout << setprecision(8) << ans;
  return 0;
}
