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

print((round(0.5*a*b)))
a,b,c = list(map(int,input().split()))

print((int(0.5*a*b)))
a, b, c = list(map(int, input().split()))
print((round(0.5 * a * b)))

a, b, c = list(map(int, input().split()))
print((int(0.5 * a * b)))

-print((round(0.5 * a * b))) +print((int(0.5 * a * b)))