#include <bits/stdc++.h>
using namespace std;
#define ll long long int
ll a[300010]={0};
int main()
{
ll n,w,i,g,b;
cin>>n>>w;
double ans=0;
for(i=1;i<=2*n;i++)
cin>>a[i];
sort(a+1,a+n+n+1);
g=a[1];
b=a[n+1];
if(b*0.5<=g)
ans=b*0.5*n+b*n;
else
ans=g*n+2*g*n;
if(ans>w)
ans=w;
cout<<setprecision(10)<<ans<<"\n";
return 0;
}
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