import java.util.Scanner;



public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
	
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		
		if(n%x==0) {
			n--;
		}
		System.out.println(((n/x)+1)*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