n=int(input())
v1=map(int,input().split())
v=list(v1)
for i in range(n):
    for j in range(i+1,n):
        if v[i]>v[j]:
            a=v[i]
            v[i]=v[j]
            v[j]=a
for l in range(n-1):
    a=(v[0]+v[1])/2
    v=a+v[2,n-l]
print(v[0])
