package main

import (
	"fmt"
)

func main() {
	var H, W uint64
	fmt.Scanf("%d %d\n", &H, &W)
	r := H / 2
  if H == 1 || W == 1 {
    fmt.Println(1)
  } else if H % 2 == 0 {
		fmt.Println(r * W)
    } else {
		i := W / 2
		j := W / 2
		if W % 2 != 0 {
			i += 1
		}
		result := (r + 1) * i + r * j
		fmt.Println(result)
    }
}
