#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<double> cup;
  int n;
  double c, w;
  scanf("%d %lf", &n, &w);
  for (int i = 0; i < n * 2; i++) {
    scanf("%lf", &c);
    cup.push_back(c);
  }
  sort(cup.begin(), cup.end());
  double maxG = cup[0];
  double maxB = cup[n];
  double ans = min(maxG, maxB / 2);
  ans = ans * (double)n * 3.0;
  if (w <= ans) {
    printf("%.7lf", w);
  } else {
    printf("%.7lf", ans);
  }
}
