#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i;
  double minm, ming, man, m;
  double a[200500];
  while (~scanf("%d%lf", &n, &m)) {
    for (i = 0; i < 2 * n; i++) scanf("%lf", &a[i]);
    sort(a, a + 2 * n);
    minm = a[n];
    ming = a[0];
    if (minm >= 2 * ming)
      man = 3 * ming * n;
    else
      man = minm * 3.0 / 2 * n;
    if (m >= man)
      printf("%f\n", man);
    else
      printf("%f\n", m);
  }
  return 0;
}
