import java.util.*;
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 time = 0;
          while(n>0){
            n = n-x;
            time += t;
          }
         System.out.println(time);
  	}
}
/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