#include "bits/stdc++.h"
#include <cassert>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pi = pair<int, int>;
using pll = pair<ll, ll>;
using pd = pair<double, double>;
using pld = pair<ld, ld>;


int main()
{
    ifstream cin("zeap.in");
    ofstream cout("zeap.out");

    auto has_at_least_2_elems = [](set<int> &nrs) -> bool
    {
        if (nrs.empty())
        {
            return false;
        }
        int aux = *begin(nrs);
        if (nrs.erase(begin(nrs)) == end(nrs))
        {
            nrs.emplace(aux);
            return false;
        }
        nrs.emplace(aux);
        return true;
    };

    set<int> nrs;
    string op;
    while (cin >> op)
    {
        if (op == "I")
        {
            int x;
            cin >> x;

            nrs.emplace(x);
        }
        else if (op == "S")
        {
            int x;
            cin >> x;

            auto it = nrs.find(x);
            if (it == end(nrs))
            {
                cout << "-1\n";
            }
            else
            {
                nrs.erase(it);
            }
        }
        else if (op == "C")
        {
            int x;
            cin >> x;

            cout << nrs.count(x) << "\n";
        }
        else if (op == "MAX")
        {
            if (has_at_least_2_elems(nrs))
            {
                cout << *prev(end(nrs)) - *begin(nrs) << "\n";
            }
            else
            {
                cout << "-1\n";
            }
        }
        else  // op = "MIN".
        {
            if (!has_at_least_2_elems(nrs))
            {
                cout << "-1\n";
                continue;
            }
            
            auto beg_it1{begin(nrs)}, beg_it2{next(begin(nrs))}, end_it1{prev(end(nrs))}, end_it2{prev(prev(end(nrs)))};
            cout << min(*beg_it2 - *beg_it1, *end_it1 - *end_it2) << "\n";
        }
    }
}