#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, w;
  int tea[200200];
  int tot;
  scanf("%d %d", &n, &w);
  tot = 2 * n;
  for (int i = 0; i < tot; i++) {
    scanf("%d", &tea[i]);
  }
  sort(tea, tea + tot);
  double suma = 0;
  if (tea[n] * 1.0 / 2 > tea[0]) {
    suma = tea[0] * 3 * n;
  } else {
    suma = tea[n] * 1.0 / 2 * 3 * n;
  }
  if (suma > w) suma = w;
  printf("%f", suma);
  return 0;
}
