Given a List L of integers, a ramp is a tuple (i, j) for which i < j and L[i] <= L[j]. The width of such a ramp is j - i. Find the maximum width of a ramp in L. If one doesn't exist, return 0. Example 1: Input: L = [6,0,8,2,1,5] Output: 4 Explanation: The maximum width ramp is achieved at (i, j) = (1, 5): L[1] = 0 and L[5] = 5. Please note 1<5 and index 4<=5. Example 2: Input: L = [9,8,1,0,2,9,4,0,4,1] Output: 7 Explanation: The maximum width ramp is achieved at (i, j) = (2, 9): L[2] = 1 and L[9] = 1.