import java.util.Scanner;
 
public class Main {
 
    public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();//目標
      	double x = sc.nextDouble();//一回あたり
      	double t = sc.nextDouble();//時間
   
    	System.out.println((int)(Math.ceil(n/x)*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