e-olymp 687

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>

using namespace __gnu_pbds;
using namespace std;

typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> indexed_set;

int main() {
    indexed_set s;
    int q, type, k;
    cin >> q;
    while (q --) {
        cin >> type >> k;
        if (type == 1)
            s.insert (k);
        else if (type == 0) {
            auto x = s.find_by_order (s.size() - k);
            cout << *x << endl;
        } else
            s.erase (s.find (k));
    }
    return 0;
}