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: 15, 21, ['J', 'b', 'T', 'K', 'h', 'H', '1073', 'Y', '9981', 'f', 'F', 'H', '623', 'b', '7921', 'm', '6545', '2415', '529', 'U', 's', 'I']

sU52924156545m7921