import java.util.*

fun main(args: Array<String>) {
    val scn = Scanner(System.`in`)
    val H = scn.nextInt()
    val W = scn.nextInt()

    if(W==1 || H == 1){
        println(1)
        return
    }

    var ans = 0L
    for(i in 1..W){
        if(i%2==1){
            ans += (H+1)/2
        }else{
            ans += H/2
        }
    }
    println(ans)
}