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: 21, 29, ['U', 'p', 's', 'q', 'J', '8545', '8509', '7371', '9265', '7585', 'J', 'P', 'Z', '6521', 'K', 'b', 'M', '2973', '515', 'a', '8115', '2019', 'O', '4877', '223', '993', '4045', '5045', 'O']

O504540459932234877O20198115