(* 1. *)

let rec spell ((i,j),mot) = 
    if mot = "" then []
                else let deb = String.sub mot 0 1 in
                     let fin = String.sub mot 1 (String.length mot -1) in
                         ((i,j),deb)::(spell ((i,j+1),fin));;


(* 2. *)

let scan_h (m,n) = 
    let rec aux (i,j) = 
        (i,j)::(if j=n then
                   if i=m then []
                          else aux (i+1,1)
                       else
                   aux (i,j+1)
               )
    in  aux (1,1);;



(* 3. *)

let scan_v (m,n) = List.map (function (i,j) -> (j,i)) (scan_h (n,m));;



(* 4. *)

let rec letters sol = match(sol) with
    []   -> []
|   t::r -> (spell t) @ (letters r);;



(* 5. *)

let rec size sol = match(letters sol) with
    [] -> (0,0)
|   ((i,j),_)::r -> let (i',j') = size r in  
         ((if i>i' then i else i'), (if j>j' then j else j'));;