#include <bits/stdc++.h>
using namespace std;
long long ara[200001];
int main() {
  long long i, j, k;
  long long l, m, n, a, b, aa;
  while (cin >> m >> n) {
    for (i = 0; i < 2 * m; i++) cin >> ara[i];
    k = m;
    k *= 2;
    sort(ara, ara + k);
    double p = (double)ara[0];
    double q = (double)ara[m];
    double low, high;
    low = 0;
    if ((q / 2) >= p)
      high = p;
    else
      high = q / 2;
    double ans;
    p = 0;
    int aaa = 0;
    while (low <= high) {
      aaa++;
      double mid = (low + high) / 2;
      ans = (m * mid) + (2 * m * mid);
      if (ans == n) break;
      if (ans > n)
        high = mid;
      else
        low = mid;
      if (abs(p - ans) < .00000001) break;
      p = ans;
    }
    cout << setprecision(10) << ans << endl;
  }
  return 0;
}
