#include <bits/stdc++.h>
using namespace std;
const int MAX = 200010;
const double EPS = 1e-6;
int a[MAX];
int main() {
  int n, w;
  scanf("%d%d", &n, &w);
  for (int i = 0; i < 2 * n; ++i) {
    scanf("%d", &a[i]);
  }
  sort(a, a + 2 * n);
  double r = min(2 * a[0], a[n]) / 2.0;
  r = r * 3 * n;
  r = min(r, (double)w);
  printf("%0.8lf\n", r);
  return 0;
}
