#include <bits/stdc++.h>
using namespace std;
int main() {
  long double n;
  int t = 0;
  long double mx, mn, l, m;
  cin >> n >> m;
  vector<long long> v(n * 2);
  for (int i = 0; i < n * 2; i++) cin >> v[i];
  cout << fixed;
  sort(v.begin(), v.end());
  mn = v[0];
  mx = v[n];
  m /= 3;
  long double girl = m / n, boy = (m * 2) / n;
  if (girl > mn) {
    boy -= (girl - mn) * 2.0;
    girl -= girl - mn;
  }
  if (boy > mx) {
    girl -= (boy - mx) / 2.0;
    boy -= (boy - mx);
  }
  cout << girl * n + boy * n;
  return 0;
}
