import java.util.*;
public class Main{
	
	
	private static Scanner sc=new Scanner(System.in);
	
	public static void main(String []args){
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		
		int time=(n/x)*t;
		if(n%x!=0)
			time+=t;
		System.out.println(time);
		
	}
	
} import java.util.*; util.* java public class Main{
	
	
	private static Scanner sc=new Scanner(System.in);
	
	public static void main(String []args){
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		
		int time=(n/x)*t;
		if(n%x!=0)
			time+=t;
		System.out.println(time);
		
	}
	
} Main private static Scanner sc=new Scanner(System.in); sc new Scanner(System.in) public static void main(String []args){
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		
		int time=(n/x)*t;
		if(n%x!=0)
			time+=t;
		System.out.println(time);
		
	} main {
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		
		int time=(n/x)*t;
		if(n%x!=0)
			time+=t;
		System.out.println(time);
		
	} int n=sc.nextInt(); n sc.nextInt() sc.nextInt sc int x=sc.nextInt(); x sc.nextInt() sc.nextInt sc int t=sc.nextInt(); t sc.nextInt() sc.nextInt sc int time=(n/x)*t; time (n/x)*t (n/x) n x t if(n%x!=0)
			time+=t; n%x!=0 n%x n x 0 time+=t time t System.out.println(time) System.out.println System.out System System.out time String []args args public class Main{
	
	
	private static Scanner sc=new Scanner(System.in);
	
	public static void main(String []args){
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		
		int time=(n/x)*t;
		if(n%x!=0)
			time+=t;
		System.out.println(time);
		
	}
	
} public class Main{
	
	
	private static Scanner sc=new Scanner(System.in);
	
	public static void main(String []args){
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		
		int time=(n/x)*t;
		if(n%x!=0)
			time+=t;
		System.out.println(time);
		
	}
	
} Main
import java.util.*;
public class Main{
	
	
	private static Scanner sc=new Scanner(System.in);
	
	public static void main(String []args){
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		
		int time=(n/x)*t;
		if(n%x!=0)
			time+=t;
		System.out.println(time);
		
	}
	
}