#include<iostream>

#include<cstdio>

#include<cstring>

#include<cstdlib>

#include<cmath>

#include<algorithm>

#include<queue>

using namespace std;

int n;

struct node

{

    int key;

    node *child[];

}bst[],*root,*pos;

queue<node*>mem;

void newnode(node* &r,int key)

{

    if(mem.empty())r=pos++;

    else r=mem.front(),mem.pop();

    r->key=key;

    r->child[]=r->child[]=NULL;

}

void insert(node* &r,int key)

{

    if(r==NULL)newnode(r,key);

    else insert(r->child[r->key<key],key);

}

bool exist(node* &r,int key)

{

    if(r==NULL)return false;

    if(r->key>key)return exist(r->child[],key);

    else return (r->key==key)||exist(r->child[],key);

}

int mmin(node* &r,int key)

{

    if(r==NULL)return key;

    if(r->key<=key)return mmin(r->child[],key);

    else

    {

        int s=mmin(r->child[],key);

        if(s==key)return r->key;

    }

}

int mmax(node* &r,int key)

{

    if(r==NULL)return key;

    if(r->key>=key)return mmax(r->child[],key);

    else

    {

        int s=mmax(r->child[],key);

        if(s==key)return r->key;

    }

}

int main()

{

    root=NULL;

    pos=bst;

    int i,j,num,ans=;

    char s[];

    scanf("%d",&n);

    for(i=;i<=n;i++)

    {

        scanf("%s",s);

        if(s[]=='I')

        {

            scanf("%d",&num);

            if(i==)

            {

                insert(root,num);

                continue;

            }

            if(root,exist(root,num))continue;

            int a=mmin(root,num),b=mmax(root,num);

            if(a==num)a=;if(b==num)b=;

            ans=min(ans,min(abs(num-a),abs(num-b)));

            insert(root,num);

        }

        else printf("%d\n",ans);

    }

}