#include<fstream>
#include<set>
#include<cstring>
using namespace std;
ifstream fin("zeap.in");
ofstream fout("zeap.out");
set<int> v;
set<int>::iterator it, it1;
int n, k;
char s[50], c[5];
int main(){
    n = 0;
    while( fin.get(s,45) ){
        n = strlen( s );
        k = -1;
        int i = 0;
        for( i = 0; i < n; i++){
            if( s[i] != ' ' ){
                c[++k] = s[i];
            }else{
                break;
            }
        }
        i++;
        int number = 0;
        for( ; i < n; i++ ){
            number = number * 10 + ( s[i] - '0' );
        }
        if( c[0] == 'I' ){
            it = v.find( number );
            if( it == v.end() ){
                v.insert( number );
            }
        }
        if( c[0] == 'S' ){
            it = v.find( number );
            if( it != v.end() ){
                v.erase( it );
            }else{
                fout << "-1\n";
            }
        }
        if( c[0] == 'C' ){
            it = v.find( number );
            if( it != v.end() ){
                fout << "1\n";
            }else{
                fout << "0\n";
            }
        }
        if( c[0] == 'M' && c[1] == 'A' ){
            if( v.size() > 1 ){
                it = v.end();
                it--;
                it1 = v.begin();
                fout << ( (*it) - (*it1) ) << "\n";
            }else{
                fout << "-1\n";
            }
        }
        if( c[0] == 'M' && c[1] == 'I' ){
            if( v.size() > 1 ){
                it = v.begin();
                it++;
                it1 = v.begin();
                fout << ( (*it) - (*it1) ) << "\n";
            }else{
                fout << "-1\n";
            }
        }
        fin.get();
    }
    return 0;
}