a=int(input())//2
b=[int(i) for i in input().split()]
for i in range(a):
    if (len(b)==1) or (len(b)==2):
        break
    del b[b.index(max(b))]
    del b[b.index(min(b))]
c=0
for i in b:
    c+=i
print(c/len(b))