
import java.util.*;

public class Main {

	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		int ans=(int)Math.ceil((double)n/x);
		//System.out.println(ans);
		System.out.println(ans*t);
	}
} import java.util.*; util.* java public class Main {

	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		int ans=(int)Math.ceil((double)n/x);
		//System.out.println(ans);
		System.out.println(ans*t);
	}
} Main public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		int ans=(int)Math.ceil((double)n/x);
		//System.out.println(ans);
		System.out.println(ans*t);
	} main {
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		int ans=(int)Math.ceil((double)n/x);
		//System.out.println(ans);
		System.out.println(ans*t);
	} 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 int ans=(int)Math.ceil((double)n/x); ans (int)Math.ceil((double)n/x) Math.ceil Math (double)n/x (double)n x System.out.println(ans*t) System.out.println System.out System System.out ans*t ans t String args[] args public class Main {

	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		int ans=(int)Math.ceil((double)n/x);
		//System.out.println(ans);
		System.out.println(ans*t);
	}
} public class Main {

	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		int ans=(int)Math.ceil((double)n/x);
		//System.out.println(ans);
		System.out.println(ans*t);
	}
} Main

import java.util.*;

public class Main {

	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int t=sc.nextInt();
		int ans=(int)Math.ceil((double)n/x);
		//System.out.println(ans);
		System.out.println(ans*t);
	}
}
