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)