#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int n, w;
  cin >> n >> w;
  long long int i, j;
  long long int s = 2 * n;
  long long int a[s];
  for (i = 0; i < 2 * n; i++) cin >> a[i];
  sort(a, a + s);
  long long int u, y;
  u = a[0];
  y = a[n];
  long long int l = 0, r = 0;
  long double p;
  p = (double)w / (3 * n);
  double x;
  if ((double)y / 2 < u) {
    x = ((double)y / (double)2);
    if (3 * n * x <= w) {
      cout << fixed << setprecision(8) << (double)(((double)y / 2) * 3 * n);
    } else
      cout << fixed << setprecision(8) << (double)w;
  } else {
    x = ((double)u);
    if (3 * n * x <= w)
      cout << fixed << setprecision(8) << (double)((u)*3 * n);
    else
      cout << fixed << setprecision(8) << (double)(w);
  }
  return 0;
}
