import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String[] tmp = sc.nextLine().split(" ");
		int n = Integer.parseInt(tmp[0]);
		double x = Integer.parseInt(tmp[1]);
		int t = Integer.parseInt(tmp[2]);

		n = (int)(Math.ceil(n / x)) * t;
		System.out.println(n);

	}

}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz