import java.util.Scanner;
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();
		int time=t;
		int x1=x;
		while(x<n)
		{
			t=t+time;
			x=x+x1;
		}
		System.out.println(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