#include<bits/stdc++.h>

using namespace std;

ifstream f("zeap.in");
ofstream g("zeap.out");

int main(){
    int val,count=0,a,b;
    string operatie;
    set<int> zeap;
    priority_queue<int, vector<int>, greater<int>> minDif;
    priority_queue<int> maxDif;
    while(f>>operatie){
        if(operatie=="I"){
            f>>val;
            zeap.insert(val);
        }
        else if(operatie=="S"){
            f>>val;
            if(zeap.count(val)==0){
                g<<-1<<"\n";
            }
            else{
                zeap.erase(val);
            }

        }
        else if(operatie=="C"){
            f>>val;
            g<<zeap.count(val)<<'\n';
        }
        else if(operatie=="MAX"){
            if(zeap.size()<2)
                g<<-1<<'\n';
            else{
                for(auto x:zeap){

                }
                //auto a=zeap.begin();
                for(auto x: zeap){
                    if(count==0){
                        a=x;
                        count++;
                    }
                    b=x;
                }
                
                g<<b-a<<'\n';
                
            }
        }
        else if(operatie=="MIN"){
            if(zeap.size()<2)
                cout<<-1<<'\n';
            else{
                for(auto x: zeap){
                    for(auto y: zeap){
                        if(x!=y){
                            minDif.push(abs(x-y));
                        }
                    }
                }
                g<<minDif.top()<<'\n';
                while(minDif.size()>0){
                    minDif.pop();
                }
                
            }
        }
        
        }
    /*for(auto x: zeap){
            cout<<x<<" ";
    }*/
    return 0;
}