Codeforces problem 5C — Longest Regular Bracket Sequence

For the below testcase, what should be the output :

(()())()(())()()())())()((()(()(())()()())((()(())()(()()()()))()(())()(((()())()(()((())()(())(()))

My answer is :

No of substring = 7 length of longest sequence = 18

Can anyone confirm because I feel codeforces test case is wrong here.?

My code : https://codeforces.com/contest/5/submission/79013600