#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  int n, w, x;
  vector<int> v;
  cin >> n >> w;
  for (int i = 0; i < 2 * n; i++) {
    cin >> x;
    v.push_back(x);
  }
  sort(v.begin(), v.end());
  double a = v[0];
  double b = 1.0 * v[n] / 2;
  double c = 1.0 * w / (3 * n);
  double ans = min(min(a, b), c) * 3 * n;
  cout << setprecision(9) << ans;
  return 0;
}
