#include <iostream>
#include <fstream>
#include <set>
#include <queue>
using namespace std;
ifstream fin("zeap.in");
ofstream fout("zeap.out");
set<int> zeap;
set<int>::iterator itr;
priority_queue<pair<int, pair<int,int>>> minn;

int main()
{
    string citire;
    while(fin>>citire)
    {
        if(citire[0]=='I')
        {
            int x;
            fin>>x;
            if(zeap.find(x)==zeap.end())
            {
                zeap.insert(x);
                auto prezent = zeap.find(x);
				auto trecut = prezent;
				trecut--;
				auto viitor = prezent;
				viitor++;
				if(prezent != zeap.begin())
                {
                    minn.push(make_pair(-abs(x - *trecut), make_pair(*trecut, x)));
                }
                if(prezent != zeap.end())
                {
                    minn.push(make_pair(-abs(*viitor - x), make_pair(*viitor, x)));
                }
            }
            /*cout << "\nThe set zeap is : \n";
            for (itr = zeap.begin(); itr != zeap.end(); itr++) {
                cout << *itr << " ";
            }*/
        }
        if(citire[0]=='S')
        {
            int x;
            fin>>x;
            if(zeap.find(x)!=zeap.end())
            {
                auto prezent = zeap.find(x);
				auto trecut = prezent;
				trecut--;
				auto viitor = prezent;
				viitor++;
				if(prezent!=zeap.begin() && viitor!=zeap.end())
                {
                    minn.push(make_pair(-abs(*viitor - *trecut), make_pair(*trecut,*viitor)));
                }
                zeap.erase(x);
            }
            else
            {
                fout << "-1"<<'\n';
            }
        }
        if(citire[0]=='C')
        {
            int x;
            fin>>x;
            if(zeap.find(x) == zeap.end())
			{
			    fout<<0<<'\n';
			}
			else
			{
			    fout<<1<<'\n';
			}

        }
        if(citire[1]=='A')
        {
            if(zeap.size()<2)
           {
               fout << "-1"<<'\n';
           }
           else
           {
                auto finall=zeap.end();
                finall--;
                fout<<*finall - *(zeap.begin())<<'\n';
           }

        }
        if(citire[1]=='I')
        {
            if(zeap.size()<2)
           {
               fout << "-1"<<'\n';
           }
            else
            {
                while(zeap.find(minn.top().second.first)==zeap.end() || zeap.find(minn.top().second.second) == zeap.end())
                {
                    minn.pop();
                }
                fout<<-minn.top().first<<'\n';
            }

        }
    }
    return 0;
}