#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9 + 5;
const int N = 2e5 + 123;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n, m;
  cin >> n >> m;
  vector<int> a(2 * n);
  for (int i = 0; i < 2 * n; ++i) {
    cin >> a[i];
  }
  sort((a).begin(), (a).end());
  double ans;
  if (a[0] * 2 <= a[n]) {
    ans = double(a[0]);
  } else {
    ans = double(a[n]) / 2.0;
  }
  if (ans * 3.0 * double(n) > m) {
    ans = m;
  } else {
    ans = ans * (3.0 * double(n));
  }
  cout << fixed << setprecision(3) << ans;
  return 0;
}
