#include <bits/stdc++.h>
using namespace std;
vector<double> a;
int main() {
  double n, w;
  scanf("%lf%lf", &n, &w);
  for (int i = 0; i < 2 * n; i++) {
    double x;
    scanf("%lf", &x);
    a.push_back(x);
  }
  sort(a.begin(), a.end());
  double b = (a[n] * n) + ((a[n] / 2) * n);
  double c = (a[0] * 2 * n) + (a[0] * n);
  double ans = min(w, min(b, c));
  printf("%f\n", ans);
  return 0;
}
