# include <bits/stdc++.h>
using namespace std;
# define db double
# define ll long long
# define pi 3.14159265359
# define rad(x) (x * pi / 180)
const int p_1[] = {1,-1};
const int mod1 = 1e9 + 7;
const int mod2 = 666013;
const int mod3 = 997;
template < class T > inline T sqr(T x) {return x*x;}
template < class T > inline T min(T a,T b,T c) {return min(a,min(b,c));}
template < class T > inline T min(T a,T b,T c,T d) {return min(min(a,b),min(b,c));}
template < class T > inline T max(T a,T b,T c) {return max(a,max(b,c));}
template < class T > inline T max(T a,T b,T c,T d) {return max(max(a,b),max(b,c));}
template < class T > inline T det(T a,T b,T c,T d) {return a * c - b * d;}
template < class T > inline T det(T s[3][3])
{
    return - s[0][0] * det(s[1][1],s[1][2],s[2][1],s[2][2]) + s[0][1] * det(s[1][0],s[1][2],s[2][0],s[2][2]) - s[0][2] * det(s[1][0],s[1][1],s[2][0],s[2][1]);
}
template < class T1 , class T2 , class T3 > inline T3 pow(T1 a,T2 b,T3 mod) {T3 ans = 1;while (b){if (b&1) ans = (1LL * ans * a) % mod;a = (1LL * a * a) % mod;b >>= 1;}return ans;}
template < class T > T phi(T n){T cnt = n,p = n,ans = n;for (T i = 2;i*i <= p;++i)if (!(cnt%i)){ans /= i;ans *= (i-1);while (!(cnt%i)) cnt /= i;}if (cnt > 1) ans /= cnt,ans *= (cnt - 1);return ans;}
template < class T > T f(T a,T b) {return a < b ? 0 : a / b + f(a / b);}
template < class T > T gcd(T a,T b) {return __gcd(a,b);}
class Reader {
  public:
    Reader(const string& filename):
            m_stream(filename),
            m_pos(kBufferSize - 1),
            m_buffer(new char[kBufferSize]) {
        next();
    }

    Reader& operator>>(int& value) {
        value = 0;
        while (current() < '0' || current() > '9')
            next();
        while (current() >= '0' && current() <= '9') {
            value = value * 10 + current() - '0';
            next();
        }
        return *this;
    }

  private:
    const int kBufferSize = 32768;

    char current() {
        return m_buffer[m_pos];
    }

    void next() {
        if (!(++m_pos != kBufferSize)) {
            m_stream.read(m_buffer.get(), kBufferSize);
            m_pos = 0;
        }
    }

    ifstream m_stream;
    int m_pos;
    unique_ptr<char[]> m_buffer;
};
set < int > s;
multiset < int > mn;
int main(void)
{
    ifstream fi("zeap.in");
    ofstream fo("zeap.out");
    string c;
    while (!fi.eof())
    {
        c = "-1";
        fi>>c;
        if (c == "-1" || c == "") return 0;
        if (c == "I")
        {
            int x;
            fi>>x;
            if (s.find(x) == s.end())
            {
                s.insert(x);
                set < int > :: iterator it = s.find(x),ur,pr;
                ur = it;++ur;
                if (it != s.end()) pr = it,--pr;
                if (it != s.begin() && ur != s.end())
                    mn.erase(mn.find(*ur - *pr));
                if (it != s.begin())
                    mn.insert(x - *pr);
                if (ur != s.end())
                    mn.insert(*ur - x);
            }
        }
        else
        if (c == "S")
        {
            int x;
            fi>>x;
            set < int > :: iterator it = s.find(x),pr,ur;
            if (it != s.end())
            {
                ur = it;pr = it;++ur;
                if (ur != s.end()) mn.erase(mn.find(*ur - x));
                if (it != s.begin())
                {
                    --pr;
                    mn.erase(mn.find(x - *pr));
                }
                if (ur != s.end() && it != s.begin())
                    mn.insert(*ur - *pr);
                s.erase(it);
            } else fo << "-1\n";
        }
        else
        if (c == "C")
        {
            int x;fi>>x;
            fo << (s.find(x) != s.end()) << '\n';
        }
        else
        if (c == "MIN")
        {
            if (mn.size()) fo << *(mn.begin()) << '\n';
            else fo << "-1\n";
        }
        else
        {
            if (s.size() <= 1) fo << "-1\n";
            else
            {
                set < int > :: iterator en = s.end();--en;
                fo << (*en - *s.begin()) << '\n';
            }
        }
    }
    return 0;
}