import java.util.*;
import java.io.*;
public class Main {
  public static void main(String[] args){
   Scanner sc = new Scanner(System.in);
   int n = sc.nextInt();
   int x = sc.nextInt();
   int t = sc.nextInt();

   int calc = n / x;
   if (n % x > 0) {
     calc++;
   }
   System.out.println(calc * t);
  }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz