import java.util.*;
import java.io.*;
public class Main {

	public static void main(String[] args) throws java.lang.Exception
    {		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st=new StringTokenizer(br.readLine());
		int n=Integer.parseInt(st.nextToken()),x=Integer.parseInt(st.nextToken()),t=Integer.parseInt(st.nextToken());
		System.out.println( (int)Math.ceil((n/(float)x))*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