Churu and lost string

Churu is taking the course called “Introduction to Data Structures”. Yesterday, he learned how to use a stack to check is a given parentheses expression is balanced or not. He finds it intriguing, and more importantly, he was given an assignment. The professor gave him a string S containing characters “(” and “)”, and asked him numerous queries of the form (x, y), i.e., if the substring S[x, y] re