#include <fstream>
#include <set>
using namespace std;
ifstream in ("zeap.in");
ofstream out ("zeap.out");
set<int> myset;
set<int>::iterator it,it2,it3;
int main ()
{
    char a;
    int k,mindif;
    while (in>>a)
    {
        if (a=='I')
        {
            in>>k;
            myset.insert(k);
        }
        if (a=='S')
        {
            in>>k;
            it=myset.find(k);
            if (it!=myset.end())
                myset.erase(it);
            else
                out<<"-1"<<'\n';
        }
        if (a=='C')
        {
            in>>k;
            it=myset.find(k);
            if (it!=myset.end())
                out<<'1'<<'\n';
            else
                out<<'0'<<'\n';
        }
        if (a=='M')
        {
            in>>a;
            if(a=='A')
            {   it2=myset.end();
                it2--;
                it3=myset.begin();
                out<<(*it2-*it3)<<'\n';
            }
            else
            {
                int b=INT_MAX;
                for (it=myset.begin();it!=--myset.end();it++)
                {
                    if(b>*++it-*--it)
                        b=*++it-*--it;
                }
                out<<b<<'\n';
            }
            in>>a;
        }
    }
    return 0;
}