import java.util.Scanner;

public class Main {

	public static void main(String[] aggs){

	Scanner stdIn = new Scanner(System.in);
	int N = stdIn.nextInt();
	int X = stdIn.nextInt();
	int T = stdIn.nextInt();

	int i=0;
	int t=0;

	for(i=0;i<N;i=i+X) {
		t=t+T;
	}

	System.out.println(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