#include<bits/stdc++.h>
using namespace std;
#define int long long
#define f(i,j,k) for(int i=j;i<=k;++i)
#define g(i,j,k) for(int i=j;i>=k;--i)
int n,m,s,l;
const int N=2e5,M=8765;
int a[N],b[N],p[N],x,y,z;string O;bool P[M][M];
inline int Q(int x,int y){return!a[y]||P[a[x]][a[y]];}
inline void put(int x){if(x)b[++m]=x;}
inline void pvt(int x){put(a[x]);put(a[x*2]);put(a[x*2+1]);}
inline void ask(){
	sort(b+1,b+m+1);m=unique(b+1,b+m+1)-b-1;
	cout<<m;f(i,1,m)cout<<" "<<b[i];cout<<endl;
	f(i,1,m)cin>>b[i];
	f(i,1,m)f(j,i,m)P[b[i]][b[j]]=1;m=0;
}
inline void mv(int x,int y){swap(a[x],a[y]);p[a[x]]=x;p[a[y]]=y;}
#define h(u,P)for(x=l;(y=x/2,z=x*2+Q(x*2+1,x*2),(x&&x<=n))&&P;x=u)
signed main(){
	cin>>s;a[0]=s+1;
	f(_,1,s*2){
		cin>>O>>l;
		if(O[0]=='a'){
			a[p[l]=++n]=l;l=n;
			h(y,1)pvt(x);ask();
			h(y,Q(x,y))mv(x,y);
		}else{
			mv(l=p[l],n);a[n--]=0;
			h(z,1)pvt(x);ask();
			h(z,Q(z,x))mv(x,z);
		}
		cout<<(n?a[1]:-1)<<endl;
	}
	return 0;
}