setmyset -- Sets in STL C++

 int main() {

/* Enter your code here. Read input from STDIN. Print output to STDOUT */

    int q, n, i, j, y, x;
    cin >> q;
    set<int> s;
    for (i=0;i<q;i++) {
        cin >> y >> x;
        if (y == 1) {
            s.insert(x);
        }
        if (y ==2) {
            s.erase(x);
        }
        if (y == 3) {
            set<int>::iterator itr = s.find(x);
            if (itr != s.end()) cout << "Yes" << endl;
            //if (*itr == x) cout << "Yes" << endl;
            else cout << "No" << endl;
        }
    }
    return 0;
}