import numpy as np

N = int(input())
V = input().split()
V = np.array(V).astype(int)
V = np.sort(V)

U = np.array([])

for _ in range(2):
    U = np.append(U, 0.5**(N-1))
    
for i in range(2, N):
    U = np.append(U, 0.5**(N-i))

print(V @ U)
