balance

let rec balance (t:'a tree) : int tree =                                                    
  let rec height t =                                                                        
    match t with                                                                            
      | Br(_,left,right) ->                                                                 
          let (hl, hr) = (height left, height right) in                                     
          if (hl > hr) then hl + 1 else hr + 1                                              
      | _ -> 0                                                                              
  in                                                                                        
  match t with                                                                              
    | Br(value, left, right) -> Br(height left - height right, balance left, balance right) 
    | Lf -> Lf                                                                              
;;