{$A+,B-,D+,E-,F-,G-,I+,L+,N+,O-,P-,Q+,R+,S+,T-,V+,X+,Y+}
Var n,i:longint;
    s:string;
BEGIN
 readln(n);
 if n=0 then begin writeln(0); exit; end;
 if n=1 then begin writeln(1); exit; end;
 s:='';
 for i:=9 downto 2 do
  while (n mod i)=0 do begin s:=chr(ord('0')+i)+s; n:=n div
i; end;
 if n<>1 then writeln(-1) else writeln(s);
END.

>  if n=0 then begin writeln(0); exit; end;

Look, i will be swearing now. What's that?
Yeah, "This problem sure contains some traps", but i would
hardly call them "good"!
So, do you consider natural (i.e. positive integer) numbers
to start from 1,2, and so on? Ok, so did i, before coming
to this place (surely very very good place). But then, i
lost many submitions, being not able to imagine, that in
that task "positive integer" means 0,1,2,...

And here it is again... As i can guess, here you consider
positive integers start from 1,2, and so on. Came to any
common solution?

Please, if you make such traps (i know, that is necessary),
make them good real traps, for people to be out of word,
being catched.

Yours, Greg