import java.util.*;

public class Main{
	public static void main(String arg[]){
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		if(n%x==0)
			System.out.println((t*(n/x)));
		else 
			System.out.println(t*((n/x)+1));
	}
}
/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