#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, w;
  vector<int> v;
  int t;
  cin >> n >> w;
  for (int i = 0; i < 2 * n; i++) {
    cin >> t;
    v.push_back(t);
  }
  sort(v.begin(), v.end());
  double d = min((double)v[0], (double)v[n] / 2);
  double dd = min(3 * n * d, (double)w);
  cout << setprecision(9) << dd;
  return 0;
}
