#include <bits/stdc++.h>
#pragma comment(linker, "/stack:336777216")
#pragma GCC optimize("O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using ui = unsigned int;
ll const mod = 1000000007;
int main() {
  ios_base::sync_with_stdio(false), cin.tie(nullptr);
  cout << setprecision(8) << fixed;
  int n, w;
  cin >> n >> w;
  vector<int> v(2 * n);
  for (int i = 0; i < 2 * n; i++) cin >> v[i];
  sort(v.begin(), v.end());
  ld s = 0.0, e = (ld)v[0], ans = -1;
  int turns = 100;
  while (turns--) {
    ld m = (s + e) / 2;
    if (2 * m <= v[n] && 3 * m * n <= w)
      ans = m, s = m;
    else
      e = m;
  }
  cout << 3 * n * ans << '\n';
  return 0;
}
