#include <fstream>
#include <queue>
#include <set>
using namespace std;
 
const int inf = 0x3f3f3f3f;
 
struct MinHeap{
    priority_queue<int, vector<int>, greater<int> > H, D;
 
    void push(int x){
        H.push(x);
    }
 
    void pop(int x){
        D.push(x);
    }
 
    int top(){
        while (!H.empty() && !D.empty() && H.top() == D.top()){
            H.pop();
            D.pop();
        }
 
        if (H.empty())
            return -1;
 
        return H.top();
    }
};
 
struct Zeap{
    set<int> S;
    MinHeap H;
 
    int size;
 
    inline set<int> :: iterator bf(set<int> :: iterator it){
        if (it != S.begin())
            --it;
        return it;
    }
 
    inline int max(){
        return *bf(S.end());
    }
 
    inline int min(){
        return *S.begin();
    }
 
    void insert(int x){
        if (S.find(x) != S.end())
            return;
 
        int st = *bf(S.lower_bound(x));
        int dr = *S.upper_bound(x);
 
        if (st && st < x)
            H.push(x - st);
        if (dr && x < dr)
            H.push(dr - x);
        if (st < x && x < dr)
            H.pop(dr - st);
 
        S.insert(x);
 
        ++size;
    }
 
    bool erase(int x){
        set<int> :: iterator it = S.find(x);
 
        if (it == S.end())
            return false;
 
        S.erase(*it);
 
        int st = *bf(S.lower_bound(x));
        int dr = *S.upper_bound(x);
 
        if (st && st < x)
            H.pop(x - st);
        if (dr && x < dr)
            H.pop(dr - x);
        if (st < x && x < dr)
            H.push(dr - st);
 
        --size;
 
        return true;
    }
 
    bool find(int x){
        return S.find(x) != S.end();
    }
 
    int smin(){
        if (size < 2)
            return -1;
        return H.top();
    }
 
    int smax(){
        if (size < 2)
            return -1;
 
        return max() - min();
    }
};
 
Zeap Z;
char s[101];
 
ifstream in("zeap.in");
ofstream out("zeap.out");
 
int main(){
    int x;
 
    while (in >> s){
        if (s[0] == 'I'){
            in >> x;
            Z.insert(x);
            continue;
        }
 
        if (s[0] == 'S'){
            in >> x;
            if (!Z.erase(x))
                out << "-1\n";
            continue;
        }
 
        if (s[0] == 'C'){
            in >> x;
            out << Z.find(x) << "\n";
            continue;
        }
 
        if (s[1] == 'I')
            out << Z.smin() << "\n";
        else
            out << Z.smax() << "\n";
    }
 
    return 0;
}