#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  float w, ans = 0.0;
  scanf("%d", &n);
  scanf("%f", &w);
  float a[2 * n];
  memset(a, 0, sizeof(a));
  for (int i = 0; i < 2 * n; i++) scanf("%f", &a[i]);
  sort(a, a + 2 * n);
  if (a[n] >= 2 * a[0]) {
    ans = a[0] * 3 * n;
  } else if (a[0] >= a[n] / (2.0))
    ans = a[n] * 1.5 * n;
  if (ans > w) ans = w;
  printf("%f", ans);
}
