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, 21, ['321', 'I', '4943', 'w', '7753', 'e', '6789', 'g', 'G', 'x', 'm', 'g', 'Q', '2199', '3643', '3055', 'v', 'u', '8743', 'H', '4643']

4643