#include <bits/stdc++.h>
using namespace std;
int n, w;
int v[200010];
int main() {
  scanf("%d%d", &n, &w);
  for (int i = 1; i <= 2 * n; ++i) scanf("%d", &v[i]);
  sort(v + 1, v + 2 * n + 1);
  double sol = min(1LL * w * 2, min(1LL * v[1] * 2, 1LL * v[n + 1]) * 3 * n);
  printf("%.6lf\n", sol / 2);
  return 0;
}
