1
var removeOuterParentheses = function (s) {
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  let open = -1,
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    ans = "",
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    stack = [];
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  for (let c of s) {
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    if (c == "(") {
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      // open for top level open
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      if (open != -1) ans += c;
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      stack.push(open);
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      open++;
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    } else {
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      open = stack.pop();
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      // close for top level open
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      if (open != -1) ans += c;
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    }
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  }
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  return ans;
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};