#include <bits/stdc++.h>
using namespace std;
int main() {
  double n, w;
  cin >> n >> w;
  double b_min = 0x6fffffff, g_min = 0x6fffffff;
  vector<int> a(2 * (int)n);
  for (int i = 0; i < 2 * n; ++i) {
    cin >> a[i];
  }
  sort(a.begin(), a.end());
  g_min = a[0];
  b_min = a[(int)n];
  double x = w / (3 * n);
  if (x > g_min) x = g_min;
  if (2 * x > b_min) x = b_min / 2;
  double r = 3 * n * x;
  printf("%.10lf\n", r);
  return 0;
}
