import java.util.*;

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