a = list(map(int,input().split()))

a.sort()

print((int(a[0]*a[1]/2)))
l = list(map(int,input().split()))

l.sort()

print((int(l[0]*l[1]/2)))
a = list(map(int, input().split()))
a.sort()
print((int(a[0] * a[1] / 2)))

l = list(map(int, input().split()))
l.sort()
print((int(l[0] * l[1] / 2)))

-a = list(map(int, input().split())) -a.sort() -print((int(a[0] * a[1] / 2))) +l = list(map(int, input().split())) +l.sort() +print((int(l[0] * l[1] / 2)))