import java.util.Scanner;

public class Main{
  public static void main(String args[]){
    Scanner scanner = new Scanner(System.in);
    double n = scanner.nextInt();
    double x = scanner.nextInt();
    double t = scanner.nextInt();

    int kaisu = (int)Math.ceil(n/x); 
    //System.out.println(kaisu);
    System.out.println((int)t*kaisu);
    
  }
}


/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