#include <fstream>
#include <algorithm>
#include <queue>
#include <set>
 
using namespace std;
 
ifstream fin("zeap.in");
ofstream fout("zeap.out");
 
set <long> zeap;
priority_queue <long, vector<long>, greater<long> > h, p;
 
void Insert_Heap(long val)
{
    h.push(val);
}
 
void Delete_Heap(long x)
{
    p.push(x);
}
 
void Insert_Zeap(long x)
{
    set <long> :: iterator it;
    if(zeap.find(x) != zeap.end()) return;
 
    it = zeap.lower_bound(x);
    if(it != zeap.begin()) it--;
    int st = *it;
    it = zeap.upper_bound(x);
    int dr = *it;
 
    if(st && st < x)
        Insert_Heap(x - st);
    if(dr && dr > x)
        Insert_Heap(dr - x);
    if(st < x && x < dr)
        Delete_Heap(dr - st);
    zeap.insert(x);
}
 
bool Delete_Zeap(int x)
{
    set <long> :: iterator it, itt;
    itt = zeap.find(x);
    if(itt == zeap.end()) return 0;
 
    zeap.erase(itt);
 
    it = zeap.lower_bound(x);
    if(it != zeap.begin()) it--;
    int st = *it;
    it = zeap.upper_bound(x);
    int dr = *it;
 
    if(st && st < x)
        Delete_Heap(x - st);
    if(dr && dr > x)
        Delete_Heap(dr - x);
    if(st < x && x < dr)
        Insert_Heap(dr - st);
    return 1;
}
 
bool Search_Zeap(long x)
{
    return zeap.find(x) != zeap.end();
}
 
void Zeap_difmin()
{
    while(h.size() && p.size() && h.top() == p.top())
    {
        h.pop();
        p.pop();
    }
    if(h.size()) fout<<h.top()<<'\n';
    else fout<<"-1\n";
}
 
void Zeap_difmax()
{
    if(zeap.size() < 2)
    {
        fout<<"-1\n";
        return;
    }
    set <long> :: iterator it = zeap.end(); it--;
    fout<<-*zeap.begin() + *it<<'\n';
}
 
int main()
{
    string s; long x;
    while(fin>>s)
    {
        if(s[0] == 'I')
        {
            fin>>x;
            Insert_Zeap(x);
        }else
        if(s[0] == 'S')
        {
            fin>>x;
            if(!Delete_Zeap(x))
                fout<<"-1\n";
        }else
        if(s[0] == 'C')
        {
            fin>>x;
            fout<<Search_Zeap(x)<<'\n';
        }else
        if(s[1] == 'I')
            Zeap_difmin();
        else
            Zeap_difmax();
    }
    return 0;
}