import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = Integer.parseInt(sc.next());
    int x = Integer.parseInt(sc.next());
    int t = Integer.parseInt(sc.next());
    
    int ans = n / x;
    if(n%x > 0){
      ans++;
    }
    ans = ans * t;

    System.out.println(ans);
   
    sc.close();
    return;
  }
  
  
}

/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