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

	static Scanner inp= new Scanner(System.in);
	static PrintWriter out= new PrintWriter(System.out);
	public static void main(String args[]) {		    	
	   	Main g=new Main();
	   	g.main();
	   	out.close();
	}

	
	
	//Main
	void main() {
		
		int n=inp.nextInt();
		int x=inp.nextInt();
		int t=inp.nextInt();
		System.out.println((((n+x-1))/x)*t);
		
	}
    
    
		
} import java.util.*; util.* java import java.io.*; io.* java public class Main {

	static Scanner inp= new Scanner(System.in);
	static PrintWriter out= new PrintWriter(System.out);
	public static void main(String args[]) {		    	
	   	Main g=new Main();
	   	g.main();
	   	out.close();
	}

	
	
	//Main
	void main() {
		
		int n=inp.nextInt();
		int x=inp.nextInt();
		int t=inp.nextInt();
		System.out.println((((n+x-1))/x)*t);
		
	}
    
    
		
} Main static Scanner inp= new Scanner(System.in); inp new Scanner(System.in) static PrintWriter out= new PrintWriter(System.out); out new PrintWriter(System.out) public static void main(String args[]) {		    	
	   	Main g=new Main();
	   	g.main();
	   	out.close();
	} main {		    	
	   	Main g=new Main();
	   	g.main();
	   	out.close();
	} Main g=new Main(); g new Main() g.main() g.main g out.close() out.close out String args[] args //Main
	void main() {
		
		int n=inp.nextInt();
		int x=inp.nextInt();
		int t=inp.nextInt();
		System.out.println((((n+x-1))/x)*t);
		
	} main {
		
		int n=inp.nextInt();
		int x=inp.nextInt();
		int t=inp.nextInt();
		System.out.println((((n+x-1))/x)*t);
		
	} int n=inp.nextInt(); n inp.nextInt() inp.nextInt inp int x=inp.nextInt(); x inp.nextInt() inp.nextInt inp int t=inp.nextInt(); t inp.nextInt() inp.nextInt inp System.out.println((((n+x-1))/x)*t) System.out.println System.out System System.out (((n+x-1))/x)*t (((n+x-1))/x) ((n+x-1)) n+x n x 1 x t public class Main {

	static Scanner inp= new Scanner(System.in);
	static PrintWriter out= new PrintWriter(System.out);
	public static void main(String args[]) {		    	
	   	Main g=new Main();
	   	g.main();
	   	out.close();
	}

	
	
	//Main
	void main() {
		
		int n=inp.nextInt();
		int x=inp.nextInt();
		int t=inp.nextInt();
		System.out.println((((n+x-1))/x)*t);
		
	}
    
    
		
} public class Main {

	static Scanner inp= new Scanner(System.in);
	static PrintWriter out= new PrintWriter(System.out);
	public static void main(String args[]) {		    	
	   	Main g=new Main();
	   	g.main();
	   	out.close();
	}

	
	
	//Main
	void main() {
		
		int n=inp.nextInt();
		int x=inp.nextInt();
		int t=inp.nextInt();
		System.out.println((((n+x-1))/x)*t);
		
	}
    
    
		
} Main
import java.util.*;
import java.io.*;
public class Main {

	static Scanner inp= new Scanner(System.in);
	static PrintWriter out= new PrintWriter(System.out);
	public static void main(String args[]) {		    	
	   	Main g=new Main();
	   	g.main();
	   	out.close();
	}

	
	
	//Main
	void main() {
		
		int n=inp.nextInt();
		int x=inp.nextInt();
		int t=inp.nextInt();
		System.out.println((((n+x-1))/x)*t);
		
	}
    
    
		
}
