#include <bits/stdc++.h>
using namespace std;
double num[200005];
int main() {
  int n;
  double w;
  scanf("%d%lf", &n, &w);
  for (int i = 0; i < 2 * n; i++) scanf("%lf", &num[i]);
  sort(num, num + 2 * n);
  double ans = ((num[0]) < (num[n] / 2.0) ? (num[0]) : (num[n] / 2.0));
  printf("%f\n", (((ans * 3 * n)) < (w) ? ((ans * 3 * n)) : (w)));
  return 0;
}
