How is a joint property divided ?

1.Namaste,I am living in a joint property which we brought it 3 years ago. 2.House description: South side-6 ft.joint stairs and disputrers house. 3.Myself and the person causing dispute has made a legal agreement at the time of sale deed that stairs belong to each of us i.e.,3 ft. for them and 3 ft. for us.We made a seperate Clause stating that stairs belong to each of us. 4.After an year the disputer has moved inside from nothern part (which was actually part of road) 5.He has filed a case in the court stating that "we are in short of land area so total 6 ft. area of stairs belong to us. 6.They actually have shortage in land area. 7.If we give away the stairs we have to close our southern side windows and doors. 8.We are ready to compensate the shortage area. what could be the ideal solution for this problem.