#include <bits/stdc++.h>
using namespace std;
const int NN = 2 * 100005;
int a[NN], w;
int main() {
  int n;
  cin >> n >> w;
  for (int i = 0; i < 2 * n; i++) cin >> a[i];
  sort(a, a + 2 * n);
  double ans = min((double)a[0], a[n] / 2.0) * 3 * n;
  if (ans > w)
    cout << w << endl;
  else
    printf("%.10lf\n", ans);
  return 0;
}
