N = int(input())
v = input().split()

for i in range(N):
    v[i] = int(v[i])
v.sort()
ite = 0
while(ite < N-1):
    v[ite+1] = (int(v[ite])+int(v[ite+1]))/2
    v[ite] = 0
    #v.sort()
    ite += 1

print(v[-1])

