#include <bits/stdc++.h>
using namespace std;
const int mod = (int)1e9 + 7;
const int inf = (int)1e9;
const int base = 10;
int main() {
  int n, w;
  cin >> n >> w;
  vector<int> a(2 * n);
  for (int i = 0; i < 2 * n; i++) cin >> a[i];
  sort(a.begin(), a.end());
  int max = a.front();
  int ma2x = a[n];
  long double x = min((long double)max, (long double)ma2x / 2);
  long double ans = min(3 * x * n, (long double)w);
  cout.precision(10);
  cout << fixed << ans;
  return 0;
}
