Untitled

#include <iostream>
#include <set>
using namespace std;
set<int> s;

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n;
    cin >> n;
    while (n--) {
        int type, x;
        cin >> type >> x;
        if (type == 1) {
            if (s.find(x) != s.end()) s.erase(x);
            else s.insert(x);
        }
        else {
            if (s.size() < 2)   cout << -1 << endl;
            else {
                set<int>::iterator rb = s.lower_bound(x+1);
                set<int>::iterator lb = prev(rb);
                cout << ((rb == s.end() || rb == s.begin()) ? -1 : *rb - *lb) << endl;
            }
        }
    }
}