#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 10;
int n;
long double w, a[N];
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n >> w;
  for (int i = 0; i < 2 * n; ++i) cin >> a[i];
  sort(a, a + 2 * n);
  cout << fixed << setprecision(10)
       << min(w, (long double)1.5 * n * min(a[0] * 2, a[n]));
}
