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


public class Main{
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
                
                int N = scan.nextInt();
                int X = scan.nextInt();
                int T = scan.nextInt();               
                
                int minute = N/X;
                int amari = N%X;
                
                if(amari!=0){
                    System.out.println(T*minute+T);
                }else{
                   System.out.println(T*minute); 
                }
        }
} import java.util.*; util.* java import java.lang.*; lang.* java public class Main{
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
                
                int N = scan.nextInt();
                int X = scan.nextInt();
                int T = scan.nextInt();               
                
                int minute = N/X;
                int amari = N%X;
                
                if(amari!=0){
                    System.out.println(T*minute+T);
                }else{
                   System.out.println(T*minute); 
                }
        }
} Main public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
                
                int N = scan.nextInt();
                int X = scan.nextInt();
                int T = scan.nextInt();               
                
                int minute = N/X;
                int amari = N%X;
                
                if(amari!=0){
                    System.out.println(T*minute+T);
                }else{
                   System.out.println(T*minute); 
                }
        } main {
		Scanner scan = new Scanner(System.in);
                
                int N = scan.nextInt();
                int X = scan.nextInt();
                int T = scan.nextInt();               
                
                int minute = N/X;
                int amari = N%X;
                
                if(amari!=0){
                    System.out.println(T*minute+T);
                }else{
                   System.out.println(T*minute); 
                }
        } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int N = scan.nextInt(); N scan.nextInt() scan.nextInt scan int X = scan.nextInt(); X scan.nextInt() scan.nextInt scan int T = scan.nextInt(); T scan.nextInt() scan.nextInt scan int minute = N/X; minute N/X N X int amari = N%X; amari N%X N X if(amari!=0){
                    System.out.println(T*minute+T);
                }else{
                   System.out.println(T*minute); 
                } amari!=0 amari 0 {
                    System.out.println(T*minute+T);
                } System.out.println(T*minute+T) System.out.println System.out System System.out T*minute+T T*minute T minute T {
                   System.out.println(T*minute); 
                } System.out.println(T*minute) System.out.println System.out System System.out T*minute T minute String[] args args public class Main{
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
                
                int N = scan.nextInt();
                int X = scan.nextInt();
                int T = scan.nextInt();               
                
                int minute = N/X;
                int amari = N%X;
                
                if(amari!=0){
                    System.out.println(T*minute+T);
                }else{
                   System.out.println(T*minute); 
                }
        }
} public class Main{
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
                
                int N = scan.nextInt();
                int X = scan.nextInt();
                int T = scan.nextInt();               
                
                int minute = N/X;
                int amari = N%X;
                
                if(amari!=0){
                    System.out.println(T*minute+T);
                }else{
                   System.out.println(T*minute); 
                }
        }
} Main
import java.util.*; 
import java.lang.*; 


public class Main{
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
                
                int N = scan.nextInt();
                int X = scan.nextInt();
                int T = scan.nextInt();               
                
                int minute = N/X;
                int amari = N%X;
                
                if(amari!=0){
                    System.out.println(T*minute+T);
                }else{
                   System.out.println(T*minute); 
                }
        }
}