import io.StdIn._
object Main extends App {
    val Array(h,w) = readLine.split(" ").map(_.toInt)
    
    val h_ceil = BigDecimal((h/2.0).ceil)
    val w_ceil = BigDecimal((w/2.0).ceil)
    val h_floor = BigDecimal((h/2.0).floor)
    val w_floor = BigDecimal((w/2.0).floor)

    if(h == 1 || w == 1) println(1)
    else {
        val output = w_ceil*h_ceil+h_floor*w_floor
        println(output.toLong)
    }
}