1 + (1 + 1) = (1 + 1) + 1, 2 + (1 + 1) = (2 + 1) + 1, 3 + (1 + 1) = (3 + 1) + 1 …u.s.w.
                    1 + (2 + 1) = (1 + 2) + 1, 2 + (2 + 1) = (2 + 2) + 1, 3 + (2 + 1) = (3 + 2) + 1 …u.s.w.
                    1 + (3 + 1) = (1 + 3) + 1, 2 + (3 + 1) = (2 + 3) + 1, 3 + (3 + 1)m = (3 + 3) + 1 …u.s.w.
                    u.s.w.. So könnte man die Regel “a + (b + 1) = (a + b) + 1” anschreiben.