#include <bits/stdc++.h>
using namespace std;
int n, w;
double tmp;
vector<double> a;
vector<double> boy;
vector<double> girl;
double volume;
double base;
int main() {
  cin >> n >> w;
  for (int i = 0; i < (2 * n); i++) {
    cin >> tmp;
    a.push_back(tmp);
  }
  sort(a.begin(), a.end());
  girl.assign(a.begin(), a.begin() + n);
  boy.assign(a.begin() + n, a.end());
  if (boy[0] / 2 > girl[0])
    base = girl[0];
  else
    base = boy[0] / 2;
  volume = (3 * base * n);
  if (volume > w) volume = w;
  cout << fixed << setprecision(10) << volume;
  return 0;
}
