#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, w;
  cout.precision(10);
  cin >> n >> w;
  vector<int> v;
  int temp;
  for (int i = 0; i < 2 * n; i++) {
    cin >> temp;
    v.push_back(temp);
  }
  sort(v.begin(), v.end(), greater<int>());
  float ma = (float)v[n - 1];
  ma /= 2;
  float ans = 0;
  if (ma <= v[2 * n - 1])
    ans = ma * 3 * n;
  else {
    ma = v[2 * n - 1];
    ans = ma * 3 * n;
  }
  if ((float)w > ans)
    cout << ans << endl;
  else {
    cout << w << endl;
  }
}
