n=input()
n=int(n)
val=list(map(int,input().strip().split(' ')))
val.sort()
res=0
if val:
    if len(val)==1:
        print(val[0]/2)
    elif len(val)==2:
        print(sun(val)/2)
    else:
        #res=(val[0]+val[1])/2
        res=(val[0]+val[1])/2
        for i in range(2,len(val)):
            res=(res+val[i])/2
            #print(res)
        print(res)
else:
    #print('error')
    pass