[jQuery] [n00b] merging input values into another input filed value

[mindprint]

I am trying to merge vaues from three different input fields into one
resulting when submitting a form. I just acn't get my head around.
This the last code that does not work for me.

            function friends() {
                                var friend1 = $(input#friend_1).val();
                                var friend2 = $(input#friend_2).val();
                                var friend3 = $(input#friend_3).val();
                     $("input#rsvp-notes").val(friend1, friend2, friend3);
                    }

Any direction much appriciated
Stan