import java.util.Scanner

fun main() {

    val scanner = Scanner(System.`in`)

    while (scanner.hasNext()) {
        val N = scanner.nextInt()
        val X = scanner.nextInt()
        val T = scanner.nextInt()

        val unit = N / X + if(N % X != 0) 1 else 0
        println(unit * T)
    }
}