#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, w, k;
  double result;
  cin >> n >> w;
  vector<long long> v;
  for (long long i = 0; i < 2 * n; i++) {
    cin >> k;
    v.push_back(k);
  }
  sort(v.begin(), v.end());
  if ((2 * v[0]) > (v[v.size() / 2])) {
    result = (v[v.size() / 2] * 1.5 * n);
  } else
    result = v[0] * 3 * n;
  if (result > w)
    cout << fixed << setprecision(6) << w;
  else
    cout << fixed << setprecision(6) << result;
  return 0;
}
