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

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

set<int> zeap;

void inserare(int x)
{
    zeap.insert(x);
}

int stergere(int x)
{
    if (zeap.count(x))
    {
        zeap.erase(x);
        return 1;
    }
    return -1;
}

int cauta(int x)
{
    return zeap.count(x);
}

int maxim()
{
    if (zeap.size() < 2)
        return -1;

    return abs(*zeap.rbegin() - *zeap.begin());
}

int minim()
{
    if (zeap.size() < 2)
        return -1;

    int minDif = INT_MAX;
    auto it = zeap.begin();
    int prev = *it;
    ++it;
    while (it != zeap.end())
    {
        minDif = min(minDif, abs(*it - prev));
        prev = *it;
        ++it;
    }

    return minDif;
}

int main()
{
    string comanda;
    int x;
    while (fin >> comanda)
    {
        if (comanda == "I")
        {
            fin >> x;
            inserare(x);
        }
        else if (comanda == "S")
        {
            fin >> x;
            int val = stergere(x);
            if (val == -1)
                fout << -1 << "\n";
        }
        else if (comanda == "C")
        {
            fin >> x;
            fout << cauta(x) << "\n";
        }
        else if (comanda == "MAX")
        {
            fout << maxim() << "\n";
        }
        else if (comanda == "MIN")
        {
            fout << minim() << "\n";
        }
    }

    fin.close();
    fout.close();
    return 0;
}