#include <iostream>
#include <string>
#include <fstream>
#include <set>

#define DN 300005
using namespace std;

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

int p=0;
string s;

multiset < int > st,min_dif;
multiset < int >::iterator it,it2;

int main()
{
    st.insert(0);
    st.insert(1<<30);
    it=st.begin();
    while(!f.eof())
    {
        int x;
        f>>s;

        //cout<<s<<endl;
        /*cout<<" Numere : \n";
        for( it = st.begin();it!=st.end();++it)
            cout<<*it<<" ";
        cout<<"\n Dif :\n";

        for( it = min_dif.begin();it!=min_dif.end();++it)
            cout<<*it<<" ";

        cout<<endl;*/

        if(s[0]=='I')
        {
            f>>x;
            if(st.size()==2)
                st.insert(x);
            else
            {
                it=st.lower_bound(x);
                it2=it;
                --it2;

                if( *it2 != 0 && *it != (1<<30) )
                    min_dif.erase ( *it - *it2 );

                if( *it != (1<<30))
                        min_dif.insert( *it - x );
                if(*it2 != 0 )
                        min_dif.insert( x - *it2 );

                st.insert(x);
            }

        }

        if(s[0]=='S')
        {

            f>>x;
            it=st.lower_bound(x);
            if( *it != x )
                {
                    g<<-1<<"\n";
                    continue;
                }
            it2=it;
            --it2;
            ++it;
            if( *it != (1<<30))
                    min_dif.erase( *it - x );
             if(*it2 != 0 )
                    min_dif.erase( x - *it2 );
            st.erase(x);

            if( *it2 != 0 && *it != (1<<30) )
                    min_dif.insert ( *it - *it2 );
        }
        if(s[0]=='M' && s[1]=='A')
        {
            it=st.begin();
            ++it;
            it2=st.end();
            --it2; --it2;

            if(st.size()>=4)
            g<<( *it2- *it )<<"\n";
                else
                    g<<"-1"<<"\n";

        }
        else
            if(s[0]=='M' && s[1]=='I')
            {
                if(min_dif.size())
                    g<< *min_dif.begin() <<"\n";
                    else
                        g<<"-1"<<"\n";
            }
        if(s[0]=='C')
        {
            f>>x;
            it=st.lower_bound(x);
            if(*it == x)
                g<<1<<"\n";
                else
                    g<<0<<"\n";
        }
        getline(f,s);
    }


    return 0;
}