import java.util.*

fun main(args: Array<String>) {
    val result = solve(Scanner(System.`in`))
    if (result.isNotEmpty()) println(result)
}

fun solve(`in`: String) = solve(Scanner(`in`))


fun solve(sc: Scanner): String {
    val H = sc.nextLong()
    val W = sc.nextLong()

    if (H == 1L || W == 1L) {
        return "1"
    }
    return ((H * W + 1) / 2).toString()
}
