#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>s;
inline void solve()
{
	int op,x;
    cin>>op>>x;
    switch(op) 
    {
        case 1:
            s.insert(x);
            break;
        case 2: 
            s.erase(x);
            break;
        case 3: 
            cout<<s.order_of_key(x)+1<< endl;
            break;
        case 4: 
            cout<<*s.find_by_order(x-1)<<endl;
            break;
        case 5: 
            cout<<*(--s.lower_bound(x))<<endl;
            break;
        case 6:
            cout<<*s.upper_bound(x)<<endl;
            break;
    }
}
signed main() 
{
    int n;
    cin>>n; 
    while(n--) 
    {
        solve();
    }

    return 0;
}

求助WA#8#9#10#11#12