#include <fstream>
#include <algorithm>
#include <queue>
#include <set>
  
using namespace std;
  
ifstream f ("zeap.in");
ofstream g ("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()) g << h.top() << '\n';
    else g << "-1\n";
}
  
void Zeap_difmax()
{
    if(zeap.size() < 2)
    {
        g << "-1\n";
        return;
    }
    set <long> :: iterator it = zeap.end(); 
	it--;
    g << -*zeap.begin() + *it << '\n';
}
  
int main()
{
    string s; 
	long x;
	
    while (f >> s)
    {
        if (s[0] == 'I')
        {
            f >> x;
            Insert_Zeap(x);
        }
		else
			if (s[0] == 'S')
			{
				f >> x;
				if (!Delete_Zeap(x))
					g << "-1\n";
			}
			else
				if (s[0] == 'C')
				{
					f >> x;
					g << Search_Zeap(x) << '\n';
				}
				else
					if (s[1] == 'I')
						Zeap_difmin();
					else
						Zeap_difmax();
    }
    return 0;
}