#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, w;
  while (~scanf("%d%d", &n, &w)) {
    int i, *a;
    a = (int *)malloc(2 * n * sizeof(int));
    double p;
    for (i = 0; i < 2 * n; i++) scanf("%d", a + i);
    sort(a, a + 2 * n);
    if (a[0] < a[n] / 2.0)
      p = a[0];
    else
      p = a[n] / 2.0;
    if (p * 3 * n < w)
      printf("%lf\n", p * 3 * n);
    else
      printf("%lf\n", w * 1.0);
  }
  return 0;
}
