import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		
		int n = stdIn.nextInt();
		int x = stdIn.nextInt();
		int t = stdIn.nextInt();
		
		System.out.println((n+x-1)/x*t);
		
		

	}

} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		
		int n = stdIn.nextInt();
		int x = stdIn.nextInt();
		int t = stdIn.nextInt();
		
		System.out.println((n+x-1)/x*t);
		
		

	}

} Main public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		
		int n = stdIn.nextInt();
		int x = stdIn.nextInt();
		int t = stdIn.nextInt();
		
		System.out.println((n+x-1)/x*t);
		
		

	} main {
		Scanner stdIn = new Scanner(System.in);
		
		int n = stdIn.nextInt();
		int x = stdIn.nextInt();
		int t = stdIn.nextInt();
		
		System.out.println((n+x-1)/x*t);
		
		

	} Scanner stdIn = new Scanner(System.in); stdIn new Scanner(System.in) int n = stdIn.nextInt(); n stdIn.nextInt() stdIn.nextInt stdIn int x = stdIn.nextInt(); x stdIn.nextInt() stdIn.nextInt stdIn int t = stdIn.nextInt(); t stdIn.nextInt() stdIn.nextInt stdIn System.out.println((n+x-1)/x*t) System.out.println System.out System System.out (n+x-1)/x*t (n+x-1)/x (n+x-1) n+x n x 1 x t String[] args args public class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		
		int n = stdIn.nextInt();
		int x = stdIn.nextInt();
		int t = stdIn.nextInt();
		
		System.out.println((n+x-1)/x*t);
		
		

	}

} public class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		
		int n = stdIn.nextInt();
		int x = stdIn.nextInt();
		int t = stdIn.nextInt();
		
		System.out.println((n+x-1)/x*t);
		
		

	}

} Main
import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		
		int n = stdIn.nextInt();
		int x = stdIn.nextInt();
		int t = stdIn.nextInt();
		
		System.out.println((n+x-1)/x*t);
		
		

	}

}
