

H, W = list(map(int, input().split()))



if H==1 or W==1:

    print((1))

else:

    if H%2==0:

        print((H*W//2))

    else:

        if W%2==0:

            print((H*W//2))

        else:

            print((H*W//2+1))

# Problem B - Bishop



import math



# input

H, W = list(map(int, input().split()))



# check

if H==1 or W==1:

    print((1))

else:

    ans = math.ceil(H * W / 2)

    print(ans)

H, W = list(map(int, input().split()))
if H == 1 or W == 1:
    print((1))
else:
    if H % 2 == 0:
        print((H * W // 2))
    else:
        if W % 2 == 0:
            print((H * W // 2))
        else:
            print((H * W // 2 + 1))

# Problem B - Bishop
import math

# input
H, W = list(map(int, input().split()))
# check
if H == 1 or W == 1:
    print((1))
else:
    ans = math.ceil(H * W / 2)
    print(ans)

+# Problem B - Bishop +import math + +# input +# check -    if H % 2 == 0: -        print((H * W // 2)) -    else: -        if W % 2 == 0: -            print((H * W // 2)) -        else: -            print((H * W // 2 + 1)) +    ans = math.ceil(H * W / 2) +    print(ans)