import java.util.*

fun main(args: Array<String>) {
    val scan = Scanner(System.`in`)
    var (n,x,t) = scan.nextLine().split(" ").map{ it.trim().toInt() }.toTypedArray()

    var ans = 0
    var c = 0
    while(ans<n)
    {
        ans+=x
        c+=t
    }
    println(c)
}
