here is code:
program Voland_1014;

var
    N, i: longint;
    s, stmp: string;
    d: boolean;
begin
    readln (N); s:='';
        if N < 2 then begin writeln (N); exit; end;
    repeat
        d:=false;
        for i:=9 downto 2 do begin
            if N mod i = 0 then begin
                d:=true;
                N := n div i;
                str (i, stmp);
                s:= stmp + s;
                break;
            end;
        end;
        if not d then begin
            writeln (-1);
            exit;
        end;
    until N=1;
    writeln (s);
end.

> here is code:
> program Voland_1014;
>
> var
>     N, i: longint;
>     s, stmp: string;
>     d: boolean;
> begin
>     readln (N); s:='';
>         if N < 2 then begin writeln (N); exit; end;
>     repeat
>         d:=false;
>         for i:=9 downto 2 do begin
>             if N mod i = 0 then begin
>                 d:=true;
>                 N := n div i;
>                 str (i, stmp);
>                 s:= stmp + s;
>                 break;
>             end;
>         end;
>         if not d then begin
>             writeln (-1);
>             exit;
>         end;
>     until N=1;
>     writeln (s);
> end.