import java.util.Scanner;
 
public class Main {
 
	public static void main(String[] args) {
 
		Scanner sc = new Scanner(System.in);
 
		int n, x, t;
 
		n = sc.nextInt();
		x = sc.nextInt();
		t = sc.nextInt();
 
		int cook = (int) Math.ceil((double) n / (double) x);
 
		System.out.println(cook * t);
 
		sc.close();
	}
 
}
/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