func sort(a){qsort(a,1,length(a))}
func qsort(a,p,r){if(p<r){q=ptn(a,p,r);qsort(a,p,q-1);qsort(a,q+1,r)}}
func ptn(a,p,r){x=a[r];i=p-1;for(j=p;j<r;j++){if(a[j]<=x){i++;t=a[i];a[i]=a[j];a[j]=t}}t=a[i+1];a[i+1]=a[r];a[r]=t;return i+1}
BEGIN{
	getline n
	getline
	for(i=1;i<=NF;i++)a[i]=$i
	sort(a)
	ans=a[1]
	for(i=2;i<=NF;i++)ans=(ans+a[i])/2
	print(ans)
}