#include <iostream>
#include<bits/stdc++.h>

using namespace std;

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

set<long long>zp;




int main()
{
    string com;
    while(fin>>com)
    {
        if(com == "I")
        {
            int x;
            fin>>x;
            zp.insert(x);
        }
        if(com == "S")
        {
            int x;
            fin>>x;
            if(zp.find(x)==zp.end())
                fout<<-1<<"\n";
            else
             zp.erase(x);
        }
        if(com == "C")
        {
            int x;
            fin>>x;
            if(zp.find(x)==zp.end())
                fout<<0<<"\n";
            else
                fout<<1<<"\n";
        }
        if(com == "MAX")
        {
            set<long long>::iterator it = zp.begin();
            set<long long>::iterator it2 = zp.end();
            it2--;
            if(zp.size()<2)
                fout<<-1<<"\n";
            else
            {
                fout<<abs(*it - *it2)<<"\n";
            }
        }
        if(com == "MIN")
        {
            set<long long>::iterator it = zp.begin();
            set<long long>::iterator it2 = zp.begin();
            it2++;
            if(zp.size()<2)
                fout<<-1<<"\n";
            else
             fout<<abs(*it-*it2)<<"\n";

        }
    }


	return 0;

}