#include <bits/stdc++.h>
using namespace std;
int pot[1000005];
int main() {
  int n;
  double w;
  scanf("%d", &n);
  scanf("%lf", &w);
  int x = 2 * n;
  for (int i = 0; i < x; i++) scanf("%d", &pot[i]);
  sort(pot, pot + x);
  int minb = pot[n];
  int ming = pot[0];
  double ans;
  if (minb >= 2 * ming) {
    ans = (ming * (3.0) * n);
    if (w < ans) {
      ans = w;
    }
  } else {
    ans = (minb * n * (1.5));
    if (w < ans) {
      ans = w;
    }
  }
  printf("%.7f", ans);
  return 0;
}
