#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, w, i;
  int g = -1, b = -1;
  int a[200100];
  double am, eps = 0.000000001, ans;
  scanf("%d%d", &n, &w);
  for (i = 1; i <= 2 * n; i++) scanf("%d", &a[i]);
  sort(a + 1, a + n + n + 1);
  for (i = 1; i <= n; i++)
    if (a[i] < g || g == -1) g = a[i];
  for (i = n + 1; i <= 2 * n; i++)
    if (a[i] < b || b == -1) b = a[i];
  if (g * 2 <= b)
    am = double(g);
  else
    am = double(b) / 2;
  if (am * double(n) * 3. + eps <= double(w))
    ans = am * double(n) * 3;
  else
    ans = double(w);
  printf("%.6lf\n", ans);
}
