#include <bits/stdc++.h>
int main() {
  int n, w;
  std::cin >> n >> w;
  long long int *volumes = new long long int[2 * n];
  for (int i = 0; i < 2 * n; ++i) {
    std::cin >> volumes[i];
  }
  std::sort(volumes, volumes + 2 * n);
  double val1 = 3 * n * volumes[0], val2 = 1.5 * n * volumes[n];
  std::cout << std::setprecision(10)
            << std::min(std::min(val1, val2), (double)w) << '\n';
}
