class Solution:
    def removeOuterParentheses(self, S: str) -> str:

        cnt = 0
        ans = ""
        begin = 0

        for i, s in enumerate(S):
            if s == "(":
                cnt += 1
            else:
                cnt -= 1
            if cnt == 0:
                ans += S[begin+1:i]
                begin = i+1
        return ans