#include<bits/stdc++.h>
using namespace std;
ifstream f("zeap.in");
ofstream g("zeap.out");
int n, x, minim=1e9;
set<int>s, t;
char a[5], p[]="MAX";
int main()
{
    while(f>>a)
    {
        if(a[0]=='I') {f>>x; s.insert(x);}
        else if(a[0]=='S')
        {
            f>>x;
            if(s.find(x)!=s.end()) s.erase(x);
            else g<<-1<<'\n';
        }
        else if(a[0]=='C')
        {
            f>>x;
            if(s.find(x)!=s.end()) g<<1<<'\n';
            else g<<0<<'\n';
        }
        else if(a[0]=='M' && a[1]=='A')
        {
            if(s.size()<2) g<<-1<<'\n';
            else
            {
                set<int>::iterator it=s.begin();
                set<int>::iterator it1=s.end();
                it1--;
                g<<*it1-*it<<'\n';
            }
        }
        else
        {
            minim=1e9;
            if(s.size()<2) g<<-1<<'\n';
            else
            {
                set<int>::iterator it=s.begin();
                it++;
                set<int>::iterator it2=s.end();
                it2--;
                for(set<int>::iterator it1=s.begin(); it1!=it2, it!=s.end(); it1++, it++)
                    if(minim>*it-*it1) minim=*it-*it1;
                g<<minim<<'\n';
            }
        }
    }
    return 0;
}