fun main(args: Array<String>) {
    val (h, w) = readLine()!!.split(' ').map { it.toLong() }

    if (h == 1L || w == 1L) {
        println(1)
    } else {
        var ans: Long = 0L
        var odd: Long = h / 2
        val even: Long = odd
        if (h % 2L == 1L) {
            odd += 1
        }

        ans += odd * (w / 2)
        ans += even * (w / 2)
        if (w % 2L == 1L) {
            ans += odd
        }

        println(ans)
    }
}
