import java.util.Scanner
import kotlin.system.exitProcess

fun main(args: Array<String>) {
	val scn = Scanner(System.`in`)
	val h = scn.nextLong()
	val w = scn.nextLong()
	if (h==1L || w==1L) {
		println(1)
		exitProcess(0)
	}
	var ans = w*(h/2)
	if (h%2!=0L) ans += (w+1)/2
	println(ans)
}