1valid(X) :- in_target(X). 
    2-valid(X) :- not valid(X).
    3
    4in_target(X) :-  X#>=0, X#=<10. 
    5in_target(X) :-  X#>4, X#<10. 
    6in_target(X) :-  X#=5. 
    7
    8member(X, [X|_]).
    9member(X, [_|R]) :- member(X, R). 
   10
   11?- -valid(X).