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 concatenate all elements of A from the ith element to the jth element, and print 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.
Input: 7, 18, ['5091', 'H', 'a', 'm', '5799', 'g', 'R', 'Y', '6807', 'J', '8779', '5389', '6151', '3503', '6829', '9781', '5797', 'U']

RY6807J8779538961513503682997815797U