#include <bits/stdc++.h>
using namespace std;
long long rdtsc() {
  long long tmp;
  asm("rdtsc" : "=A"(tmp));
  return tmp;
}
inline int myrand() { return abs((rand() << 15) ^ rand()); }
inline int rnd(int x) { return myrand() % x; }
const int INF = (int)1e9 + 1;
const long double EPS = 1e-9;
void precalc() {}
const int maxn = (int)1e5 + 10;
int a[2 * maxn];
int n, w;
bool read() {
  if (scanf("%d%d", &n, &w) < 2) {
    return 0;
  }
  for (int i = 0; i < 2 * n; ++i) {
    scanf("%d", &a[i]);
  }
  return 1;
}
void solve() {
  sort(a, a + 2 * n);
  printf("%.18f\n",
         min((double)w, min((double)a[n] / 2, (double)a[0]) * 3 * n));
}
int main() {
  srand(rdtsc());
  precalc();
  while (1) {
    if (!read()) {
      break;
    }
    solve();
  }
  return 0;
}
