#include <bits/stdc++.h>
using namespace std;
void answer() {
  long long n, m, a, b;
  cin >> n >> m;
  double ans = 0;
  std::vector<long long> v(2 * n);
  for (int i = 0; i < 2 * n; i++) cin >> v[i];
  sort(v.begin(), v.end());
  if (v[0] < v[n] * 1.0 / 2)
    ans += n * v[0] * 3.0;
  else
    ans += n * v[n] * 3.0 / 2;
  cout << std::setprecision(7) << min((double)m, ans) << "\n";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int q;
  answer();
  return 0;
}
