N = int(input())
v = list(map(int,input().split()))
v.sort()

while len(v) >= 2:
    if len(v) % 2 == 0:
        newv = [(v[i] + v[i+1])/2 for i in range(0,len(v)-1,2)]
        v = newv
    else:
        f = v[len(v)-1]        
        newv = [(v[i] + v[i+1])/2 for i in range(0,len(v)-2,2)]
        v = newv
        v.append(f)

if len(v) == 1:
    print(v[0])