from math import ceil

h,w=list(map(int,input().split()))

ans=0

if h==1 or w==1:

    ans=1

elif (h*w)%2==0:

    ans=int(h*w//2)

else:

    ans=ceil(h*w/2)

print(ans)
from math import ceil

h,w=list(map(int,input().split()))

ans=0

if h==1 or w==1:

    ans=1

else:

    ans=ceil(h*w/2)

print(ans)
from math import ceil

h, w = list(map(int, input().split()))
ans = 0
if h == 1 or w == 1:
    ans = 1
elif (h * w) % 2 == 0:
    ans = int(h * w // 2)
else:
    ans = ceil(h * w / 2)
print(ans)

from math import ceil

h, w = list(map(int, input().split()))
ans = 0
if h == 1 or w == 1:
    ans = 1
else:
    ans = ceil(h * w / 2)
print(ans)

-elif (h * w) % 2 == 0: -    ans = int(h * w // 2)