#include <bits/stdc++.h>
using namespace std;
vector<int> A;
int main() {
  int n, w;
  scanf("%d %d", &n, &w);
  A.resize(2 * n);
  for (int i = 0; i < 2 * n; ++i) {
    scanf("%d", &A[i]);
  }
  sort(A.begin(), A.end());
  double min_quan = (w * 1.0) / (n * 3.0);
  for (int i = 0; i < n; ++i) {
    min_quan = min(min_quan, double(A[i]));
  }
  for (int i = n; i < 2 * n; ++i) {
    min_quan = min(min_quan, A[i] / 2.0);
  }
  cout.precision(10);
  cout << fixed << 3.0 * n * min_quan;
  return 0;
}
