import java.util.*; 
import java.lang.*; 


public class Main{
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
                
                int N = scan.nextInt();
                int X = scan.nextInt();
                int T = scan.nextInt();               
                
                int minute = N/X;
                int amari = N%X;
                
                if(amari!=0){
                    System.out.println(T*minute+T);
                }else{
                   System.out.println(T*minute); 
                }
        }
}
/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