
import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner ob=new Scanner(System.in);
		long n=ob.nextLong();
		long x=ob.nextLong();
		long t=ob.nextLong();
		long ans=(long)Math.ceil(n*(1.0)/x);
		System.out.println(ans*t);
	}
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner ob=new Scanner(System.in);
		long n=ob.nextLong();
		long x=ob.nextLong();
		long t=ob.nextLong();
		long ans=(long)Math.ceil(n*(1.0)/x);
		System.out.println(ans*t);
	}
} Main public static void main(String[] args) {
		Scanner ob=new Scanner(System.in);
		long n=ob.nextLong();
		long x=ob.nextLong();
		long t=ob.nextLong();
		long ans=(long)Math.ceil(n*(1.0)/x);
		System.out.println(ans*t);
	} main {
		Scanner ob=new Scanner(System.in);
		long n=ob.nextLong();
		long x=ob.nextLong();
		long t=ob.nextLong();
		long ans=(long)Math.ceil(n*(1.0)/x);
		System.out.println(ans*t);
	} Scanner ob=new Scanner(System.in); ob new Scanner(System.in) long n=ob.nextLong(); n ob.nextLong() ob.nextLong ob long x=ob.nextLong(); x ob.nextLong() ob.nextLong ob long t=ob.nextLong(); t ob.nextLong() ob.nextLong ob long ans=(long)Math.ceil(n*(1.0)/x); ans (long)Math.ceil(n*(1.0)/x) Math.ceil Math n*(1.0)/x n*(1.0) n (1.0) 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 ob=new Scanner(System.in);
		long n=ob.nextLong();
		long x=ob.nextLong();
		long t=ob.nextLong();
		long ans=(long)Math.ceil(n*(1.0)/x);
		System.out.println(ans*t);
	}
} public class Main {

	public static void main(String[] args) {
		Scanner ob=new Scanner(System.in);
		long n=ob.nextLong();
		long x=ob.nextLong();
		long t=ob.nextLong();
		long ans=(long)Math.ceil(n*(1.0)/x);
		System.out.println(ans*t);
	}
} Main

import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner ob=new Scanner(System.in);
		long n=ob.nextLong();
		long x=ob.nextLong();
		long t=ob.nextLong();
		long ans=(long)Math.ceil(n*(1.0)/x);
		System.out.println(ans*t);
	}
}
