#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, w, i, j, foo;
  cin >> n >> w;
  vector<int> a;
  for (i = 0; i < 2 * n; i++) {
    cin >> foo;
    a.push_back(foo);
  }
  sort(a.begin(), a.end());
  int girl = a[0];
  int boy = min(a[n], 2 * girl);
  double val = (double)boy / (double)2;
  double z = (double)(val * 3 * n);
  if (z <= (double)w)
    printf("%.6lf\n", z);
  else
    printf("%.6lf\n", (double)w);
  return 0;
}
