#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, w;
  cin >> n >> w;
  vector<long long> v;
  for (int i = 0; i < 2 * n; i++) {
    long long c;
    cin >> c;
    v.push_back(c);
  }
  double ans1, ans2;
  sort(v.begin(), v.end());
  if (v[n] >= v[0] * 2) {
    ans1 = v[0];
    ans2 = 2 * v[0];
  } else {
    ans1 = (double)(v[n]) / 2;
    ans2 = v[n];
  }
  cout << fixed;
  double ans = n * (ans1 + ans2);
  if (ans < w)
    cout << ans << endl;
  else
    cout << w << endl;
}
