n = int(input())
lv = sorted(list(map(int, input().split())))

dps = 0

while len(lv) > 1:
    i = 1
    j = 0
    prev = lv[j]
    ld = []
    while len(lv) > i:
        ld.append([(lv[i] - prev), j, i])
        prev = lv[i]
        j = i
        i += 1

    ld = sorted(ld, key=lambda x: x[0])
    #print(ld)
    #print(lv)

    a = lv.pop(ld[0][1])
    b = lv.pop(ld[0][2] - 1)
    lv = list(map(lambda x: 2*x, lv))
    lv.append((a+b))
    
    lv = sorted(lv)

    dps += 1

print(lv[0] / (2**dps))

