#include <bits/stdc++.h>
using namespace std;
ifstream fi("zeap.in");
ofstream fo("zeap.out");

const int INF = 1000000001;

char A[100];
set <int> S;
multiset <int> D;

int main()
{
    S.insert(-INF);
    S.insert(INF);
    D.insert(2 * INF);

    while (fi >> A + 1) {
        if (A[1] == 'I') {
            int x;
            fi >> x;

            auto it = S.upper_bound(x);
            it--;
            if (*it != x) {
                it++;
                int prev, nxt;
                nxt = *it;
                it--;
                prev = *it;

                auto it2 = D.upper_bound(nxt - prev);
                it2--;

                D.erase(it2);
                S.insert(x);
                D.insert(nxt - x);
                D.insert(x - prev);
            }
        }
        else if (A[1] == 'S') {
            int x;
            fi >> x;

            auto it = S.upper_bound(x);
            it--;

            if (*it == x) {
                int prev, nxt;
                it++;
                nxt = *it;

                it--;
                it--;
                prev = *it;
                it++;
                S.erase(it);

                auto it2 = D.upper_bound(nxt - x);
                it2--;
                D.erase(it2);

                it2 = D.upper_bound(x - prev);
                it2--;
                D.erase(it2);
                D.insert(nxt - prev);
            }
            else {
                fo << -1 << "\n";
            }
        }
        else if (A[1] == 'C') {
            int x;
            fi >> x;

            auto it = S.upper_bound(x);
            it--;

            if (*it == x) {
                fo << 1 << "\n";
            }
            else {
                fo << 0 << "\n";
            }
        }
        else if (A[1]=='M' && A[2] == 'A') {
            if (S.size() < 4)
                fo << -1 << "\n";
            else {
                int rez = 0;
                auto it = S.end();
                it--;
                it--;

                rez = *it;
                it = S.begin();
                it++;
                rez -= (*it);
                fo << rez << "\n";
            }
        }
        else if (A[1] == 'M' && A[2] == 'I') {
            if (S.size() < 4)
                fo << -1 << "\n";
            else {
                auto it = D.begin();
                fo << (*it) << "\n";
            }
        }
    }

    return 0;

}