class Solution:
    def solve(self, H: int, W: int) -> int:

        if H == 1 or W == 1:
            return 1
        else:
            return (H*W + 1) // 2


if __name__ == '__main__':

    # standard input
    H, W = map(int, input().split())

    # solve
    solution = Solution()
    print(solution.solve(H, W))
