import java.util.*;
public class Main{
	
	
	private static Scanner sc=new Scanner(System.in);
	
	public static void main(String []args){
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		
		int time=(n/x)*t;
		if(n%x!=0)
			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