#include <iostream>
#include <fstream>
#include <set>
#include <string>
using namespace std;

ifstream in("zeap.in");
ofstream out("zeap.out");

set<int> zeap;
set<pair<int, pair<int, int>>> difs;
string input;
int num;

void insert()
{
    in >> num;
    if (zeap.find(num) == zeap.end())
    {
        zeap.insert(num);
        auto it = zeap.find(num);
        if (it != zeap.begin())
        {
            auto stg = --it;
            difs.insert(make_pair(num - *stg, make_pair(num, *stg)));
        }
        if (it != zeap.end())
        {
            auto dr = ++it;
            difs.insert(make_pair(*dr - num, make_pair(*dr, num)));
        }
    }
}

void sterge()
{
    in >> num;
    auto it = zeap.find(num);
    if (it == zeap.end())
        out << "-1\n";
    else
    {
        zeap.erase(num);
    }
}

void cauta()
{
    in >> num;
    if (zeap.find(num) == zeap.end())
        out << "-1\n";
    else
        out << "0\n";
}

void maxdif()
{
    if (zeap.size() < 2)
        out << "-1\n";
    else
        out << *(--zeap.end()) - *(zeap.begin()) << '\n';
}

void mindif()
{
    if (zeap.size() < 2)
        out << "-1\n";
    else
        out << "0\n";
}

int main()
{
    while (in >> input)
    {
        if (input == "I")
            insert();
        if (input == "S")
            sterge();
        if (input == "C")
            cauta();
        if (input == "MAX")
            maxdif();
        if (input == "MIN")
            mindif();
    }
    return 0;
}