#include<cstdio>
#include<set>
using namespace std;
int x,poz;
char T[20],*p;
set<int> S,D;
set<int>::iterator it,it2,it3;
int main()
{
	freopen("zeap.in","r",stdin);
	freopen("zeap.out","w",stdout);
	for(;fgets(T,20,stdin);)
	{
	    if(T[0]=='I')
	    {
	        p=T+2; x=0;
	        while(*p>='0' && *p<='9') x=x*10+*p-'0',p++;
	        it=S.find(x);
	        if(it==S.end())
	        {
	            S.insert(x); it=S.find(x);
	            if(S.size()>1)
	            {
	                it3=it; it3++;
	                it2=it; it2--;
	                if(it==S.begin()) D.insert(*it3-*it);
	                else if(it3==S.end()) D.insert(*it-*it2);
	                else
	                {
	                    D.erase(D.find(*it3-*it2));
	                    D.insert(*it-*it2);
	                    D.insert(*it3-*it);
	                }
	            }
	        }
	    }
	    else if(T[0]=='S')
	    {
	        p=T+2; x=0;
	        while(*p>='0' && *p<='9') x=x*10+*p-'0',p++;
	        it=S.find(x);
	        if(it==S.end()) printf("-1\n");
	        else
	        {
	            if(S.size()>1)
	            {
	                it3=it; it3++;
	                it2=it; it2--;
	                if(it==S.begin()) D.erase(D.find(*it3-*it));
	                else if(it3==S.end()) D.erase(D.find(*it-*it2));
	                else
	                {
	                    D.insert(*it3-*it2);
	                    D.erase(D.find(*it-*it2));
	                    D.erase(D.find(*it3-*it));
	                }
	            }
	            S.erase(it);
	        }
	    }
	    else if(T[0]=='C')
	    {
	        p=T+2; x=0;
	        while(*p>='0' && *p<='9') x=x*10+*p-'0',p++;
	        it=S.find(x);
	        if(it==S.end()) printf("0\n"); else printf("1\n");
	    }
	    else if(T[1]=='A')
	    {
	        if(S.size()<2) printf("-1\n");
	        else
	        {
	            it3=S.end(); it3--;
	            it2=S.begin();
	            printf("%d\n",*it3-*it2);
	        }
	    }
	    else
	    {
	        if(S.size()<2) printf("-1\n");
	        else printf("%d\n",*D.begin());
	    }
	}
	return 0;
}