#include <bits/stdc++.h>
using namespace std;
const int maxn = 100010;
int a[maxn * 2];
int main() {
  int n, w;
  scanf("%d%d", &n, &w);
  w *= 2;
  for (int i = 0; i < n * 2; ++i) scanf("%d", &a[i]), a[i] *= 2;
  sort(a, a + n * 2);
  int t = min(a[0], a[n] / 2);
  long long ans;
  if ((long long)t * 3 * n > (long long)w)
    ans = w;
  else
    ans = (long long)t * n * 3;
  printf("%.7lf", ans / 2.0);
  return 0;
}
