Monotonically Decreasing Subsequences

Describe an O(n^2) dynamic programming algorithm to find the length of the longest monotonically (strictly) decreasing subsequence(s) of n integers. For example, given sequence (2,4,1,3) (n=4), the decreasing subsequences are (4,1), (2,1), (4,3), (2), (4), (1), and (3), so your algorithm should return 2 for this example.