Definition: In this task, you are given inputs i, j, and A, where i and j are integers and A is a list. You need to find all elements of A from the ith element to the jth element, reverse the order in which they occur, and then concatenate them to output the resultant string. i and j will be non-negative, and will always have a value less than the length of A. i will always be less than j. Perform the operations in order, i.e., do not concatenate the elements and then reverse the string.
Input: 5, 20, ['n', '2879', 'h', 'x', '2827', '2711', '5577', 'u', '2589', '2715', 'b', 'M', '4821', 'g', 'x', 'N', '4773', 'U', '4949', 'y', '8769']

y4949U4773Nxg4821Mb27152589u557727112827