def main():

    #from sys import stdin, setrecursionlimit

    #setrecursionlimit(10**9)

    #r = input()

    #n = int(input())

    #a, b = map(int, input().split())

    #s, y = input().split()

    #a = input().split()

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

    #a = [input().split() for i in range(n)]

    #a = [int(input()) for i in range(n)]

    #a = [list(map(int, input().split())) for i in range(n)]

    #a = [int(s) - 1 for s in input().split()]

    #l=[int(input()) for _ in range(int(input()))]

    #res = 0

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

    if h == 1 or w == 1:

        print((1))

        return 0

    res = h*w//2

    if (h*w)%2 != 0:

        res += 1

    print(res)



if __name__ == '__main__':

    main()



def main():

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

    if h == 1 or w == 1:

        print((1))

        return 0

    print(((h*w+1)//2))



if __name__ == '__main__':

    main()



def main():
    # from sys import stdin, setrecursionlimit
    # setrecursionlimit(10**9)
    # r = input()
    # n = int(input())
    # a, b = map(int, input().split())
    # s, y = input().split()
    # a = input().split()
    # a = list(map(int, input().split()))
    # a = [input().split() for i in range(n)]
    # a = [int(input()) for i in range(n)]
    # a = [list(map(int, input().split())) for i in range(n)]
    # a = [int(s) - 1 for s in input().split()]
    # l=[int(input()) for _ in range(int(input()))]
    # res = 0
    h, w = list(map(int, input().split()))
    if h == 1 or w == 1:
        print((1))
        return 0
    res = h * w // 2
    if (h * w) % 2 != 0:
        res += 1
    print(res)


if __name__ == "__main__":
    main()

def main():
    h, w = list(map(int, input().split()))
    if h == 1 or w == 1:
        print((1))
        return 0
    print(((h * w + 1) // 2))


if __name__ == "__main__":
    main()

-    # from sys import stdin, setrecursionlimit -    # setrecursionlimit(10**9) -    # r = input() -    # n = int(input()) -    # a, b = map(int, input().split()) -    # s, y = input().split() -    # a = input().split() -    # a = list(map(int, input().split())) -    # a = [input().split() for i in range(n)] -    # a = [int(input()) for i in range(n)] -    # a = [list(map(int, input().split())) for i in range(n)] -    # a = [int(s) - 1 for s in input().split()] -    # l=[int(input()) for _ in range(int(input()))] -    # res = 0 -    res = h * w // 2 -    if (h * w) % 2 != 0: -        res += 1 -    print(res) +    print(((h * w + 1) // 2))