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

public class Main
{
	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		double n=sc.nextDouble();
		double x=sc.nextDouble();
		double t=sc.nextDouble();
		double a=Math.ceil(n/x);
		System.out.println((int)(a*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