N=int(input())
v=[int(i) for i in input().split()]
n=N-2
v.sort(reverse=True)
for i in range(n):
    x=v.pop()
    y=v.pop()
    alc=(x+y)/2
    for j in range(len(v)-1,0,-1):
        if v[i]>=alc: v.insert(v[i],alc)
    if N-i-1!=len(v):v.insert(0,alc)
print((v[0]+v[1])/2)