#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 5;

set<int> zeap;

int main() {
    freopen("zeap.in", "r", stdin);
    freopen("zeap.out", "w", stdout);
    string op;
    while (cin >> op) {
        if (op == "I") {
            int x;
            cin >> x;
            zeap.insert(x);
        } else if (op == "S") {
            int x;
            cin >> x;
            if (zeap.find(x) != zeap.end()) {
                zeap.erase(x);
            } else {
                cout << -1 << '\n';
            }
        } else if (op == "C") {
            int x;
            cin >> x;
            if (zeap.find(x) != zeap.end()) {
                cout << 1 << '\n';
            } else {
                cout << 0 << '\n';
            }
        } else if (op == "MAX") {
            if (zeap.size() < 2) {
                cout << -1 << '\n';
            } else {
                int max_dif = *(--zeap.end()) - *(zeap.begin());
                cout << max_dif << '\n';
            }
        } else if (op == "MIN") {
            if (zeap.size() < 2) {
                cout << -1 << '\n';
            } else {
                int min_dif = INT_MAX;
                for (auto it = zeap.begin(); next(it) != zeap.end(); ++it) {
                    min_dif = min(min_dif, abs(*next(it) - *it));
                }
                cout << min_dif << '\n';
            }
        }
    }
    return 0;
}