import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
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();
 		if(n%x==0)
 			System.out.println((n/x)*t);
 		else
 			System.out.println(((n/x)*t)+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