#include<fstream>
#include<algorithm>
#include<set>
#include<stdlib.h>
#include<iostream>
using namespace std;

int v[50010], s[50010], m[50010];

ifstream in("zeap.in");
ofstream out("zeap.out");
int N, K;
set<int> Set;
int main()
{
	char c;
	int nr;
	while (in >> c)
	{
		if (c == 'I')
		{
			in >> nr;
			Set.insert(nr);
		}
		else if (c == 'S')
		{
			in >> nr;
			if(Set.erase(nr)==0)
				out << "-1\n";
		}
		else if(c=='C')
		{
			in >> nr;
			if (Set.find(nr) == Set.end())
				out << "0\n";
			else
				out << "1\n";
		}
		else
		{
			in >> c;

			if (c == 'A')
			{
				if (Set.size() >= 2)
					out << abs(*(Set.rbegin()) - *(Set.begin()))<<'\n';
				
				else
					out << "-1\n";
			}
			else if(c == 'I')
			{
				if (Set.size() >= 2)
				{
					int nr1 = 1 << 30;
					int nr2 = 1 << 30;
					int mn = 1 << 30;
					for (auto i = Set.begin();i != Set.end();++i)
					{
						if (nr1 == (1 << 30))
							nr1 = *i;
						else
						{
							nr2 = *i;
						    mn = min(mn, abs(nr1 - nr2));
							nr1 = nr2;
						}
					}
					out << mn<<'\n';
				}
				else
					out << "-1\n";
			}
			in >> c;
		}
	}

	return 0;
}