import kotlin.math.*
import java.util.*
import java.io.*
fun main() {
    val A = readLine()!!.split(" ").map { it.toInt() }
    val N = A[0]
    val X = A[1]
    val T = A[2]
    if(N%X == 0){
        println(( N / X ) * T)
    }
    else{
    println((N / X + 1) * T)
    }
}