i( [],_,0 ).
i( _,[],0 ).
i( [A|R],[A|S],W ) :- i( R,S,P ), W is P + 1.
i( [_|R],[_|S],W ) :- i( R,S,P ), W is P.


:-i( [1,2,3,4],[1,3,2,4],I ),writeln(I).
:-i( [1,2,3,4],[1,2,3,4],I ),writeln(I).
:-i( [4,3,2,1],[1,2,3,4],I ),writeln(I).
:-i( [1,1,1,1],[2,2,2,2],I ),writeln(I).