1541

class Solution {
public:
    int minInsertions(string s) {
        int open, ans;
        open = ans = 0;
        for(int i=0; i<s.length(); i++){
            if(s[i] ==  '(') open++;
            if(s[i] == ')'){
                if(i+1 < s.length() && s[i+1] == ')') i++;
                else ans++;
                if(open>0)open--;
                else ans++;
            }
        }
        return ans + (open*2);
    }
};