#include <bits/stdc++.h>
#define BUF_SIZE 1 << 14

int end = 0, cnt;
char buf[BUF_SIZE];
int pbuf=BUF_SIZE;
FILE*fi,*fo;
inline char nextch(){
    if(pbuf == cnt && cnt < BUF_SIZE) return EOF;
    if(pbuf == BUF_SIZE){
        cnt = fread(buf, 1, BUF_SIZE, fi);
        pbuf = 0;
    }
    return buf[pbuf++];
}
inline int nextnum(){
    int a = 0;
    char c = nextch();
    while(!isdigit(c))
        c = nextch();
    while(isdigit(c)){
        a = a * 10 + c - '0';
        c = nextch();
    }
    return a;
}

std::set <int> mySet;
int count;
std::multiset <int> diff;
int main(){
    fi = fopen("zeap.in","r");
    fo = fopen("zeap.out","w");

    char c = nextch();
    while(c == 'I' || c == 'S' || c == 'C' || c == 'M'){
        if(c == 'I'){
            int x = nextnum();
            auto it = mySet.find(x);
            if(it == mySet.end()){
                if(count >= 1){
                    if(x < *mySet.begin())
                        diff.insert(*mySet.begin() - x);
                    else if(x > *mySet.rbegin())
                        diff.insert(x - *mySet.rbegin());
                    else{
                        auto it1 = mySet.lower_bound(x), it2 = mySet.upper_bound(x);
                        it1--;
                        diff.erase(diff.find(*it2 - *it1));
                        diff.insert(x - *it1);
                        diff.insert(*it2 - x);
                    }
                }
                count++;
                mySet.insert(x);
            }
        }
        else if(c == 'S'){
            int x = nextnum();
            auto it = mySet.find(x);
            if(it != mySet.end()){
                if(count >= 2){
                    if(x == *mySet.begin()){
                        auto it = mySet.begin(); it++;
                        diff.erase(diff.find(*it - x));
                    }
                    else if(x == *mySet.rbegin()){
                        auto it = mySet.rbegin(); it--;
                        diff.erase(diff.find(x - *it));
                    }
                    else{
                        auto it1 = mySet.lower_bound(x), it2 = mySet.upper_bound(x);
                        it1--;
                        diff.insert(*it2 - *it1);
                        diff.erase(diff.find(x - *it1));
                        diff.erase(diff.find(*it2 - x));
                    }
                }
                count--;
                mySet.erase(it);
            }
            else
                fprintf(fo,"-1\n");
        }
        else if(c == 'C'){
            int x = nextnum();
            auto it = mySet.find(x);
            if(it != mySet.end())
                fprintf(fo,"1\n");
            else
                fprintf(fo,"0\n");
        }
        else{
            c = nextch();
            if(count < 2)
                fprintf(fo,"-1\n");
            else if(c == 'A')
                fprintf(fo,"%d\n", *mySet.rbegin() - *mySet.begin());
            else
                fprintf(fo,"%d\n", *diff.begin());
            nextch();
            nextch();
        }
        c = nextch();
    }

    fclose(fi);
    fclose(fo);
    return 0;
}