import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		try(Scanner scanner = new Scanner(System.in)) {
			String data = scanner.nextLine();

			String[] arr = data.split(" ");
			int n = Integer.parseInt(arr[0]);
			int x = Integer.parseInt(arr[1]);
			int t = Integer.parseInt(arr[2]);

			int index = 0;
			int res = n;
			while(res > 0) {
				res = res - x;
				index++;
			}

			System.out.println(index * t);
		}
	}
}

/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