import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner reader = new Scanner(System.in);
		int N = reader.nextInt(), X = reader.nextInt(), T = reader.nextInt();
		System.out.println((int) Math.ceil(((double) N) / X) * T);
		reader.close();
	}
	
} import java.util.*; util.* java public class Main {

	public static void main(String[] args) {
		Scanner reader = new Scanner(System.in);
		int N = reader.nextInt(), X = reader.nextInt(), T = reader.nextInt();
		System.out.println((int) Math.ceil(((double) N) / X) * T);
		reader.close();
	}
	
} Main public static void main(String[] args) {
		Scanner reader = new Scanner(System.in);
		int N = reader.nextInt(), X = reader.nextInt(), T = reader.nextInt();
		System.out.println((int) Math.ceil(((double) N) / X) * T);
		reader.close();
	} main {
		Scanner reader = new Scanner(System.in);
		int N = reader.nextInt(), X = reader.nextInt(), T = reader.nextInt();
		System.out.println((int) Math.ceil(((double) N) / X) * T);
		reader.close();
	} Scanner reader = new Scanner(System.in); reader new Scanner(System.in) int N = reader.nextInt() N reader.nextInt() reader.nextInt reader X = reader.nextInt() X reader.nextInt() reader.nextInt reader T = reader.nextInt(); T reader.nextInt() reader.nextInt reader System.out.println((int) Math.ceil(((double) N) / X) * T) System.out.println System.out System System.out (int) Math.ceil(((double) N) / X) * T (int) Math.ceil(((double) N) / X) Math.ceil Math ((double) N) / X ((double) N) X T reader.close() reader.close reader String[] args args public class Main {

	public static void main(String[] args) {
		Scanner reader = new Scanner(System.in);
		int N = reader.nextInt(), X = reader.nextInt(), T = reader.nextInt();
		System.out.println((int) Math.ceil(((double) N) / X) * T);
		reader.close();
	}
	
} public class Main {

	public static void main(String[] args) {
		Scanner reader = new Scanner(System.in);
		int N = reader.nextInt(), X = reader.nextInt(), T = reader.nextInt();
		System.out.println((int) Math.ceil(((double) N) / X) * T);
		reader.close();
	}
	
} Main
import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner reader = new Scanner(System.in);
		int N = reader.nextInt(), X = reader.nextInt(), T = reader.nextInt();
		System.out.println((int) Math.ceil(((double) N) / X) * T);
		reader.close();
	}
	
}
