fun main(args: Array<String>) {
    val l = readLine()!!.split(" ").map{ it.toLong() }
    val h = l[0]
    val w = l[1]
    if (h == 1L || w == 1L) {
        println(1)
        return
    }
    val cOdd: Long
    val cEven: Long
    if (h % 2L == 0L) {
        cOdd = h/2L
        cEven = cOdd
    } else {
        cOdd = (h+1L)/2L
        cEven = cOdd - 1L
    }
    if (w % 2L == 0L) {
        println((cOdd+cEven)*w/2L)
    } else {
        println((cOdd+cEven)*(w-1)/2L + cOdd)
    }
}