The most optimal length is achieved if no parentheses need to be removed, but sometimes parentheses must be removed to maintain the balanced property. This happens when encountering a ) before a matching (. To solve this, traverse the string from left to right. Every time you encounter a (, increment the open parentheses count by one. If you encounter a ), the count of open parentheses must be at least one. If it is, decrement the count by one and increment your result by two (one for the ( and one for the ) because both are part of the remaining valid string). If not, it means you have to remove this closing parenthesis.

def solve():
    s = input()
    result = opened = 0

    for ch in s:
        if ch == '(':
            opened += 1
        elif opened:
            result += 2
            opened -= 1

    print(result)


if __name__ == "__main__":
    solve()

     

To solve this problem we have to use stack

def solve():
     

To solve this problem we have to use stack

def solve():
     

To solve this problem we have to use stack

def solve():
     

To solve this problem we have to use stack

def solve():