#include <bits/stdc++.h>
using namespace std;
const int N = (int)(1e5);
int n, w, a[N << 1];
int main() {
  cin >> n >> w;
  for (int i = 0; i < (n << 1); ++i) cin >> a[i];
  sort(a, a + (n << 1));
  double girls = min(w * 1.0 / (n * 3.0), min(a[0] * 1.0, a[n] * 0.5));
  double res = n * 3.0 * girls;
  printf("%.15lf\n", res);
  return 0;
}
