Merge three .gif animations

I have 3 .gifs animations and I just want to merge them temporally. Say g1.gif contains images 1,2,3 sequenced as so g2.gif contains images 4,5,6 sequenced as so g3.gif contains images 7,8,9 sequenced as so I want a gif as follows g4.gif contains images 1,2,3,4,5,6,7,8,9 sequenced as so I tried convert *.gif g4.gif but it overlaps them in a weird fashion. All gifs are the same size, arranging, etc Thank you so much