N = int(input())
a = map(int, input().split())
# N = 3
# a = [200, 300, 500]

s = sorted(a)
t = 0
result = 0
if len(s) == 1:
    result = s[0]
    
for i in range(0, N-1):
    if i == N - (N - 1):
        result = (t + s[i+1]) / 2
    z = (s[i] + s[i+1]) / 2
    t = z
print(result)