#include <bits/stdc++.h>
using namespace std;
const double pi = 2 * acos(0);
const int mod = 1000000007;
const int N = 1e5 + 7;
void solve() {
  int n, w;
  cin >> n >> w;
  vector<int> a(2 * n);
  for (int i = 0; i < (int)2 * n; i++) cin >> a[i];
  sort(a.begin(), a.end());
  double l = a[0];
  double r = a[n];
  double x;
  if (2 * l <= r)
    x = l;
  else
    x = r / 2;
  printf("%0.6lf\n", min((double)w, n * x + n * 2 * x));
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int q = 1;
  while (q--) {
    solve();
  }
  return 0;
}
