n = int(input())
a = [int(x) for x in input().split()]

res = 0
if len(a) % 2 != 0:
  res = a[len(a) // 2]
else:
  res = (a[len(a) // 2] + a[len(a) // 2 + 1]) / 2

print('{0:.1f}'.format(res))