#include<bits/stdc++.h>
#define deb(x) cerr << #x << ':' << x << '\n';
using namespace std;
const int N = 8005;
int sz,ev[N],es,h[N],rl[N],pos[N],n,qr[100],qsz,id[N];
void askctr(){
	cout << qsz << ' ';
	for(int i = 1;i<=qsz;i++){
		cout << qr[i] << ' ';
	}
	cout << endl;
	for(int i = 1,x;i<=qsz;i++){
		cin >> x;
		pos[x] = i;
	}
}
int main(){
	pos[0] = N;
	cin >> n;
	int nt2 = n<<1,x,p,ap;
	char op[10];
	for(int qi = 1;qi<=nt2;qi++){
		cin >> op >> x;
		if(op[0]=='a'){
			if(es)p = ev[es--];
			else p = ++sz;
			qsz = 0;
			ap = p;
			h[ap] = x;
			while(ap){
				qr[++qsz] = h[ap];
				if(h[ap^1])qr[++qsz] = h[ap^1];
				ap>>=1;
			}
			askctr();
			while(p!=1&&pos[x]<pos[h[p>>1]]){
				rl[p>>1] = p;
				h[p] = h[p>>1];
				id[h[p]] = p;
				p>>=1;
			}
			h[p] = x;
			id[x] = p;
			if(p!=1)rl[p>>1] = (pos[x]<pos[h[p^1]]?p:p^1);
		}else{
			p = ap = id[x];
//			deb(id[x]);
			qsz = 0;
			while(rl[ap]){
				h[ap] = h[rl[ap]];
				id[h[ap]] = ap;
				if(h[ap^1]){
					qr[++qsz] = h[ap];
					qr[++qsz] = h[ap^1];
				}
				ap = rl[ap];
			}
			h[ap] = 0;
			ev[++es] = ap;
			rl[ap>>1] = (h[ap^1]?ap^1:0);
			askctr();
			while(ap!=p){
				ap>>=1;
				rl[ap>>1] = (pos[h[ap]]<pos[h[ap^1]]?ap:ap^1);
			}
		}
		if(h[1])cout << h[1] << endl;
		else cout << -1 << endl;
	}
	return 0;
}