number_1 = int(input('Enter four numbers with "Enter": '))
number_2 = int(input())
number_3 = int(input())
number_4 = int(input())

sum1 = number_1 + number_2
sum2 = number_3 + number_4
result_numb = sum1 / sum2

print("%.2f" % result_numb)