count numbers present in intervals

class CountIntervals {
public:
    set<pair<int,int>> x;
    CountIntervals() {

    }

    void add(int left, int right) {
        int flag=0;
        auto it=x.begin();
        for(auto v:x)
        {

            if(v.first<=left&&left<=v.second&&v.second<right)  {x.erase(it);left=v.first;flag=1;}
            else if(left<v.first&&v.first<=right&&right<=v.second)  {x.erase(it);right=v.second;flag=1;}
            else if(left<v.first&&v.second<right)  {x.erase(it);flag=1;}
            it++;

        }
       cout<<flag<<endl;
        x.insert(make_pair(left,right));

    }

    int count() {
       int count=0;
        for(auto v:x)
        {

            count+=v.second-v.first+1;
        }
        return count;
    }
};

/**
 * Your CountIntervals object will be instantiated and called as such:
 * CountIntervals* obj = new CountIntervals();
 * obj->add(left,right);
 * int param_2 = obj->count();
 */