#include <bits/stdc++.h>
using namespace std;
map<double, int> Freq;
int main() {
  double N;
  double W;
  scanf("%lf%lf", &N, &W);
  vector<double> vec;
  for (int i = 0; i < N * 2; i++) {
    double a;
    scanf("%lf", &a);
    vec.push_back(a);
  }
  sort((vec).begin(), (vec).end());
  double ans = min(vec[0] * 1.0, vec[(int)(N + 1e-9)] / 2.0);
  ans = min(ans, W * 1.0 / (N * 3.0));
  printf("%.9lf\n", 3 * N * ans);
  return 0;
}
