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: 18, 21, ['N', 'b', 'K', 'U', 'Y', '3503', '9659', '4535', 'H', '9331', 'P', '115', '9071', 'H', 'Z', 'L', '1619', 'C', 'u', 'r', '8757', 'R', 'y']

8757ruC