count = int(input())
numbers = sorted(map(int, raw_input().split(" ")))

answer = 0
if count % 2 == 0:
    target = int(numbers[count // 2 - 1]) + int(numbers[count // 2])
else:
    target = int(numbers[count // 2]) * 2

answer = target / (2 * 1.0)
print(answer)