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

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

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