N = int(input())
v = list(map(int,input().split()))
cnt = N

while cnt is not 1:
		
    titi = max(v)
    haha = min(v)

    v.remove(titi)
    v.remove(haha)

    son = (titi + haha)/2 
    
    cnt = N - 1
    
print(son)