#include <bits/stdc++.h>
using namespace std;
const int INF = 1000 * 1000 * 1000;
const int MOD = 1000 * 1000 * 1000 + 7;
const long INF_L = 1000 * 1000 * 1000;
const long long INF_LL = 1LL * INF_L * INF_L;
const long long MOD_LL = 1000000000007LL;
long long gcd(long long a, long long b) {
  while (b) {
    a %= b;
    swap(a, b);
  }
  return a;
}
long long lcm(long long a, long long b) { return (a / gcd(a, b)) * b; }
long long pow(long long n, long long pow, long long mod) {
  long long res = 1;
  while (pow > 0) {
    if (pow & 1) {
      res = (res * n) % mod;
    }
    n = (n * n) % mod;
    pow >>= 1;
  }
  return res;
}
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());
  cout << fixed;
  cout << setprecision(6)
       << min((double)w, 3.0 * n * min((double)a[0], a[n] * 0.5)) << endl;
  return 0;
}
