let rec nlist n = if n = 0 then [] else n::nlist (n-1)
    let rec mnlist m n = if m = 0 then [] else (ignore (nlist n); mnlist (m-1) n)
    (* let m = 2000*1000 and n = 500 ;; *)
    let m = 1 and n = 850*1000*1000 ;;

    print_endline ("m=" ^ (string_of_int m) ^ " n=" ^ (string_of_int n)) ;
    mnlist m n