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

entrada.sort()

cat1 = entrada[0]

cat2 = entrada[1]

print((int(cat1*cat2/2)))

triangulo = eval(input())

lados = triangulo.split()

AB = lados[0]

BC = lados[1]

area = (int(AB) * int(BC))/2

print(("%.0f" % area))
entrada = [int(x) for x in input().split()]
entrada.sort()
cat1 = entrada[0]
cat2 = entrada[1]
print((int(cat1 * cat2 / 2)))

triangulo = eval(input())
lados = triangulo.split()
AB = lados[0]
BC = lados[1]
area = (int(AB) * int(BC)) / 2
print(("%.0f" % area))

-entrada = [int(x) for x in input().split()] -entrada.sort() -cat1 = entrada[0] -cat2 = entrada[1] -print((int(cat1 * cat2 / 2))) +triangulo = eval(input()) +lados = triangulo.split() +AB = lados[0] +BC = lados[1] +area = (int(AB) * int(BC)) / 2 +print(("%.0f" % area))