#include <bits/stdc++.h>
using namespace std;
void ifree() { freopen("in", "r", stdin); }
void ofree() { freopen("out", "w", stdout); }
double min(double a, double b) { return a < b ? a : b; }
int main() {
  int n, w;
  while (cin >> n >> w) {
    int arr[2 * n];
    for (int i = 0; i < 2 * n; i++) cin >> arr[i];
    sort(arr, arr + 2 * n);
    double ans;
    if (2 * arr[0] < arr[n])
      ans = 3 * n * arr[0];
    else
      ans = 3 * n * ((double)arr[n]) / 2;
    printf("%lf\n", min((double)w, ans));
  }
}
