N = int(raw_input())
A = map(int, raw_input().split())

A.sort()

if N % 2 == 1:
    result = 1.0 * A[N / 2]
else:
    result = 1.0 * (A[N / 2] + A[N / 2 - 1]) / 2

print "%0.5f" % (result + 0.1)