n = int(input())
v = list(map(int,input().split()))
v.sort(reverse=True)
if n == 2:
    print((v[0]+v[1])/2)
else:
    for i in range(n-1):
        p = (v[-1] + v[-2])/2
        v.pop(-1)
        v.pop(-1)
        v.append(p)
        v.sort()
    print(v[0])