What does the following Prolog program do$?$ Give all the answers Prolog would respond with for the query mystery $(x,Y,[1,2,3]).$

mystery$([],$ List, List$).$

mystery$([$H $|$ List$1],$ List$2,[$H $|$ List$3])$ :$-$

mystery$($List$1,$ List$2,$ List$3).$