N = int(input())
V = [float(v) for v in input().split()]
V.sort(revese=True)
for i in range(N):
    if len(V) == 1:
        print(V[0])
        exit()
    v1 = V.pop()
    v2 = V.pop()
    V.append((v1 + v2) / 2)
