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);
	}

} import java.util.*; util.* java import java.io.*; io.* java 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);
	}

} 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);
	} main {		
		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);
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) StringTokenizer st=new StringTokenizer(br.readLine()); st new StringTokenizer(br.readLine()) int n=Integer.parseInt(st.nextToken()) n Integer.parseInt(st.nextToken()) Integer.parseInt Integer st.nextToken() st.nextToken st x=Integer.parseInt(st.nextToken()) x Integer.parseInt(st.nextToken()) Integer.parseInt Integer st.nextToken() st.nextToken st t=Integer.parseInt(st.nextToken()); t Integer.parseInt(st.nextToken()) Integer.parseInt Integer st.nextToken() st.nextToken st System.out.println( (int)Math.ceil((n/(float)x))*t) System.out.println System.out System System.out (int)Math.ceil((n/(float)x))*t (int)Math.ceil((n/(float)x)) Math.ceil Math (n/(float)x) n (float)x t String[] args args 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);
	}

} 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);
	}

} Main
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);
	}

}