AB, BC, CA = list(map(int, input().split()))

print((int(AB * BC / 2)))

length1, length2, length3 = list(map(int, input().split()))

area = length1 * length2 / 2

print((int(area)))
AB, BC, CA = list(map(int, input().split()))
print((int(AB * BC / 2)))

length1, length2, length3 = list(map(int, input().split()))
area = length1 * length2 / 2
print((int(area)))

-AB, BC, CA = list(map(int, input().split())) -print((int(AB * BC / 2))) +length1, length2, length3 = list(map(int, input().split())) +area = length1 * length2 / 2 +print((int(area)))