import java.util.*;
 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 a = 0;
      
      if(n%x > 0) a = 1;
      System.out.println(((n / x) + a )* 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