#include <bits/stdc++.h>
using namespace std;
int main() {
  double mc, w, bc, gc;
  long int n, a[200001];
  cin >> n >> w;
  for (int i = 1; i <= 2 * n; i++) cin >> a[i];
  sort(a + 1, a + 2 * n + 1);
  gc = a[1];
  bc = a[n + 1];
  if (bc >= 2 * gc) mc = gc;
  if (bc < 2 * gc) {
    if (bc == gc)
      mc = gc / 2;
    else
      mc = bc / 2;
  }
  if (w < 2 * mc) mc = w / 2;
  if (mc * 3 * n > w)
    cout << w;
  else {
    cout.precision(9);
    cout << (mc * 3 * n);
  }
}
