#include <bits/stdc++.h>
using namespace std;
double a[2 * 100005];
const double eps = 1e-6;
double minn(double x, double y) {
  if (x - y > eps)
    return y;
  else
    return x;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n, w;
  scanf("%d %d", &n, &w);
  for (int i = 0; i < 2 * n; i++) scanf("%lf", &a[i]);
  sort(a, a + 2 * n);
  double x = minn(a[0], a[n] / 2);
  double res = 3 * n * x;
  res = minn(w, res);
  printf("%.7lf\n", res);
  return 0;
}
