import java.util.*;
 
public class Main{
	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
      	double N = sc.nextDouble();
      	double X = sc.nextDouble();
      	int T = sc.nextInt();
      	int res = (int)(Math.ceil(N/X));
      	
      	System.out.println(res*T);
    }
} import java.util.*; util.* java public class Main{
	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
      	double N = sc.nextDouble();
      	double X = sc.nextDouble();
      	int T = sc.nextInt();
      	int res = (int)(Math.ceil(N/X));
      	
      	System.out.println(res*T);
    }
} Main public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
      	double N = sc.nextDouble();
      	double X = sc.nextDouble();
      	int T = sc.nextInt();
      	int res = (int)(Math.ceil(N/X));
      	
      	System.out.println(res*T);
    } main {
    	Scanner sc = new Scanner(System.in);
      	double N = sc.nextDouble();
      	double X = sc.nextDouble();
      	int T = sc.nextInt();
      	int res = (int)(Math.ceil(N/X));
      	
      	System.out.println(res*T);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double N = sc.nextDouble(); N sc.nextDouble() sc.nextDouble sc double X = sc.nextDouble(); X sc.nextDouble() sc.nextDouble sc int T = sc.nextInt(); T sc.nextInt() sc.nextInt sc int res = (int)(Math.ceil(N/X)); res (int)(Math.ceil(N/X)) Math.ceil Math N/X N X System.out.println(res*T) System.out.println System.out System System.out res*T res T String[] args args public class Main{
	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
      	double N = sc.nextDouble();
      	double X = sc.nextDouble();
      	int T = sc.nextInt();
      	int res = (int)(Math.ceil(N/X));
      	
      	System.out.println(res*T);
    }
} public class Main{
	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
      	double N = sc.nextDouble();
      	double X = sc.nextDouble();
      	int T = sc.nextInt();
      	int res = (int)(Math.ceil(N/X));
      	
      	System.out.println(res*T);
    }
} Main
import java.util.*;
 
public class Main{
	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
      	double N = sc.nextDouble();
      	double X = sc.nextDouble();
      	int T = sc.nextInt();
      	int res = (int)(Math.ceil(N/X));
      	
      	System.out.println(res*T);
    }
}