A reversal inverts the order of the genes between index i and index j, for some i and j > i. For example, for the chromosome h5, 9, 6, 2, 1, 4, 7, 3, 8i we could get the result h6, 9, 5, 2, 1, 4, 7, 3, 8i or h5, 9, 6, 4, 1, 2, 7, 3, 8i from a reversal. How many different reversals are there for a 1000-gene chromosome?