#include<cstdio>
#include<utility>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<cassert>
#include<ctime>
using namespace std;


FILE *fin = freopen("zeap.in", "r", stdin);
FILE *fout = freopen("zeap.out", "w", stdout);

const int INF = 1000000001;
char S[20];

struct Node{
    int val;
    int MIN;
    int MAX;
    int minDIFF;
    long long priority;
    Node* left;
    Node* right;
};
Node* emptyNode = new Node;

void recompute(Node* root)
{
    if (root == emptyNode)  return;

    root -> minDIFF = INF;
    root -> MIN = root -> MAX = root -> val;

    if (root -> left != emptyNode)
        {
            root -> minDIFF = min(min(root -> val - root -> left -> MAX, root -> left -> minDIFF), root -> minDIFF);
            root -> MIN = min(root -> MIN, root -> left -> MIN);
            root -> MAX = max(root -> left -> MAX, root -> MAX);
        }
    if (root -> right != emptyNode)
        {
            root -> minDIFF = min(min(root -> right -> minDIFF, root -> right -> MIN - root -> val), root -> minDIFF);
            root -> MIN = min(root -> right -> MIN, root -> MIN) ;
            root -> MAX = max(root -> right -> MAX, root -> MAX);
        }
}

pair < Node*, Node* > split(Node* node, int val)
{
    pair < Node*, Node* > p;
    if (node == emptyNode)
    {
        p.first = emptyNode;
        p.second = emptyNode;
    }
    else
    if (val < node -> val)
    {
        pair < Node*, Node* > q = split(node -> left, val);
        p.first = q.first;
        node -> left = q.second;
        p.second = node;
        recompute(node);
    }
    else
    {
        pair < Node*, Node* > q = split(node -> right, val);
        p.second = q.second;
        node -> right = q.first;
        p.first = node;
        recompute(node);
    }

    return p;
}

bool Search(Node* node, int val)
{
    if (node == emptyNode)
        return 0;
    if (node -> val == val)
        return 1;
    if (node -> val < val)
        return Search(node -> right, val);
    return Search(node -> left, val);
}

Node* join(Node* first, Node* second)
{
    if (first == emptyNode)
        return second;
    else if (second == emptyNode)
        return first;
    else if (first -> priority < second -> priority)
    {
        first -> right = join(first -> right, second);
        recompute(first);
        return first;
    }
    else
    {
        second -> left = join(first, second -> left);
        recompute(second);
        return second;
    }
}

Node* Insert(Node* node, int val)
{
    Node* newNode = new Node;
    newNode -> val = newNode -> MIN = newNode -> MAX = val;
    newNode -> minDIFF = INF;
    newNode -> priority = ((long long) rand() << 45)
                        ^ ((long long) rand() << 30)
                        ^ ((long long) rand() << 15)
                        ^ ((long long) rand() <<  0);
    newNode -> priority &= 0x7fffffffffffffff;
    newNode -> left = emptyNode;
    newNode -> right = emptyNode;

    pair < Node*, Node* > p = split(node, val);
    return join(join(p.first, newNode), p.second);
}

Node* Delete(Node* node, int val)
{
    pair < Node*, Node* > p = split(node, val);
    pair < Node*, Node* > q = split(p.first, val - 1);

    return join(q.first, p.second);
}

int getNumber()
{
    int ind = 2, number = 0;
    while (S[ind] >= '0' && S[ind] <= '9')
        number = number * 10 + S[ind] - '0', ind++;
    return number;
}

void print(Node* root, int depth = 0) {
  if (root != emptyNode) {
    for(int i = 0; i < depth; i++)
      printf("  ");
    printf("%d:  %lld\n", root->val, root->priority);
    print(root->left, depth + 1);
    print(root->right, depth + 1);
  }
  if (depth == 0)
    printf("\n");
}

int main()
    {
        emptyNode -> val = emptyNode -> MAX = -INF;
        emptyNode -> MIN = emptyNode -> minDIFF = INF;
        emptyNode -> priority = -1;
        emptyNode -> left = emptyNode;
        emptyNode -> right = emptyNode;

        Node* root = emptyNode;

        while(gets(S))
        {
            if (S[0] != 'M')
            {
                int number = getNumber();
                if (S[0] == 'I')
                {
                    if (!Search(root, number))
                        root = Insert(root, number);
                }
                if (S[0] == 'S')
                {
                    if (Search(root, number))
                        root = Delete(root, number);
                    else
                        printf("-1\n");
                }
                if (S[0] == 'C')
                    printf("%d\n", Search(root, number));
            }
            else
            {
                if (S[1] == 'I')
                {
                    int diff = root -> minDIFF;
                    if (diff == INF)
                        printf("-1\n");
                    else
                        printf("%d\n", diff);
                }
                else
                {
                    int diff = root -> MAX - root -> MIN;
                    if (diff < 1)
                        printf("-1\n");
                    else
                        printf("%d\n", diff);
                }
            }
        }
}