import java.util.*;
class Main
{
	public static void main(String []args)
	{
		Scanner scan = new Scanner(System.in);
		int N,X,T;
		N = scan.nextInt();
		X = scan.nextInt();
		T = scan.nextInt();
		
		int count  = N/X;
		
		if(N%X == 0)
		{
			System.out.print(count*T);
		}
		else
		{
			System.out.print((count+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