#include <iostream>
#include <fstream>
#include <cstring>
#include <vector>
#include <queue>
#include <set>

using namespace std;

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

set<int>z;

priority_queue<pair<int,pair<int,int>>, vector<pair<int,pair<int,int>>>, greater<pair<int,pair<int,int>>> > d;


int main()
{
    int x;
    char c;
    char s[5];

    while(f>>s)
    {
        c = s[0];
        if(c == 'I')
        {
            f>>x;
            z.insert(x);
            auto i = z.find(x);

            if(i!=z.begin())
            {
                i--;
                d.push({x-*i,{*i,x}});
                i++;

            }
            if(++i!=z.end())
            {
                d.push({*i-x,{*i,x}});
            }
        }
        if(c == 'S')
        {
            f >> x;
            if(z.find(x) != z.end())
            {
                auto i = z.find(x);
                auto j = ++i;
                i--;
                auto k = --i;
                d.push({*j - *k, {*j, *k}});
                z.erase(x);
            }
            else
            {
                g << -1 << endl;
            }
        }
        if(c == 'C')
        {
            f >> x;
            if(z.find(x) == z.end())
                g << 0 << endl;
            else
                g << 1 << endl;
        }
        if(c == 'M')
        {
            c = s[2];
            if(c == 'N')
            {
                if(z.size() < 2)
                    g << -1 << endl;
                else
                {
                    while(!d.empty() && (z.find(d.top().second.first) == z.end() || z.find(d.top().second.second) == z.end()))
                    {
                        d.pop();
                    }
                    g << d.top().first << endl;
                }
            }
            if(c == 'X')
            {
                if(z.size() < 2)
                    g << -1 << endl;
                else
                {
                    g << *(--z.end()) - *(z.begin()) << endl;
                }
            }
        }
    }

}