import java.util.*;

public class Main{
	public static void main(String arg[]){
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		if(n%x==0)
			System.out.println((t*(n/x)));
		else 
			System.out.println(t*((n/x)+1));
	}
} import java.util.*; util.* java public class Main{
	public static void main(String arg[]){
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		if(n%x==0)
			System.out.println((t*(n/x)));
		else 
			System.out.println(t*((n/x)+1));
	}
} Main public static void main(String arg[]){
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		if(n%x==0)
			System.out.println((t*(n/x)));
		else 
			System.out.println(t*((n/x)+1));
	} main {
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		if(n%x==0)
			System.out.println((t*(n/x)));
		else 
			System.out.println(t*((n/x)+1));
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) 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 if(n%x==0)
			System.out.println((t*(n/x)));
		else 
			System.out.println(t*((n/x)+1)); n%x==0 n%x n x 0 System.out.println((t*(n/x))) System.out.println System.out System System.out (t*(n/x)) t (n/x) n x System.out.println(t*((n/x)+1)) System.out.println System.out System System.out t*((n/x)+1) t ((n/x)+1) (n/x) n x 1 String arg[] arg public class Main{
	public static void main(String arg[]){
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		if(n%x==0)
			System.out.println((t*(n/x)));
		else 
			System.out.println(t*((n/x)+1));
	}
} public class Main{
	public static void main(String arg[]){
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		if(n%x==0)
			System.out.println((t*(n/x)));
		else 
			System.out.println(t*((n/x)+1));
	}
} Main
import java.util.*;

public class Main{
	public static void main(String arg[]){
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		if(n%x==0)
			System.out.println((t*(n/x)));
		else 
			System.out.println(t*((n/x)+1));
	}
}