#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  long long int w, n, i, a[200010], mn = 1e9, x, c, n2, ans;
  cin >> n >> w;
  n2 = n << 1;
  for (i = 0; i < n2; i++) {
    cin >> a[i];
    if (mn > a[i]) mn = a[i];
  }
  for (i = 0, c = 0; i < n2; i++) {
    if (a[i] >= 2 * mn) c++;
  }
  if (c >= n) {
    if (3 * n * mn >= w)
      cout << w << endl;
    else
      cout << 3 * n * mn << endl;
  } else {
    sort(a, a + n2);
    x = a[n];
    ans = n * x + n * x / 2;
    if (ans >= w)
      cout << w << endl;
    else if (x % 2 && n % 2)
      cout << ans << ".5" << endl;
    else
      cout << ans << endl;
  }
  return 0;
}
