import java.util.Scanner;

fun main (args : Array<String>) {
  val input = Scanner(System.`in`)
  
  while (input.hasNext()) {
    val N = input.nextInt()
    val X = input.nextInt()
    val T = input.nextInt()
    val unit = N / X + if (N % X != 0) 1 else 0
    
    println (unit * T)
  }  
}