#include <bits/stdc++.h>
using namespace std;
long long n, w, a[200005];
double ans;
int main() {
  scanf("%I64d%I64d", &n, &w);
  for (int i = 1; i <= n + n; i++) scanf("%I64d", a + i);
  sort(a + 1, a + n + n + 1);
  ans = min(min((double)((long long)a[1] * 3 * n), a[n + 1] * n * 1.5),
            (double)w);
  printf("%.10f\n", ans);
  return 0;
}
