#include <bits/stdc++.h>
using namespace std;
int n, w;
int a[200001];
int main() {
  scanf("%d%d", &n, &w);
  for (int i = 0; i < 2 * n; ++i) scanf("%d", a + i);
  sort(a, a + 2 * n);
  double mn = 1e9;
  for (int i = 0; i < 2 * n; ++i) {
    if (i < n)
      mn = min(a[i] * 1.0, mn);
    else
      mn = min(a[i] * 0.5, mn);
  }
  printf("%.10f\n", min(w * 1.0, mn * 3.0 * n));
  return 0;
}
