#include <bits/stdc++.h>
using namespace std;
int n;
long long int w, x[200005];
int main() {
  cin >> n >> w;
  for (int i = 0; i < n * 2; i++) cin >> x[i];
  sort(x, x + n * 2);
  double mid;
  mid = min((double)x[n] / 2, (double)x[0]);
  mid = (mid + mid * 2) * n;
  mid = min(mid, (double)w);
  printf("%.6f\n", mid);
}
