#include<bits/stdc++.h>
using namespace std;
const int N = 100100;
int read(){
	int x;scanf("%d",&x);return x;
}
int lc[N],rc[N],top[N],rt[N],val[N],n,size = 0;
int update(int u,int l,int r,int pos,int key)
{
	int p = ++size;
	lc[p] = lc[u];rc[p] = rc[u];
	if(l == r) {val[p] = key;return p;}
	int mid = l + r >> 1;
	if(pos <= mid) lc[p] = update(lc[u],l,mid,pos,key);
	else rc[p] = update(rc[u],mid+1,r,pos,key);
	return p;
}
int ask(int u,int l,int r,int pos)
{
	if(l == r) {return val[u];}
	int mid = l + r >> 1;
	if(pos <= mid) return ask(lc[u],l,mid,pos);
	else return ask(rc[u],mid+1,r,pos);
}
int main()
{
	n = read();
	for(int i = 1;i <= n;i++)
	{
		char ch[5];
		scanf("%s",ch);
		
		if(ch[0] == 'a')
		{
			int x = read();
			top[i] = top[i-1] + 1;
			rt[i] = update(rt[i-1],1,top[i],top[i],x);
		}
		if(ch[0] == 's')
		{	
			top[i] = top[i-1];
			rt[i] = rt[i-1];
//			cout<<"top[i] "<<top[i]<<endl;
			rt[i] = update(rt[i-1],1,top[i],top[i],0);
			top[i]--;

			
		}
		if(ch[0] == 't')
		{
			int x = read();
			rt[i] = rt[x-1];top[i] = top[x-1];
		}
		printf("%d\n",top[i] == 0?-1:ask(rt[i],1,top[i],top[i]));
		for(int j = 1;j <= top[i];j++)
		{
		cout<<"j:: "<<j<<" "<<ask(rt[i],1,top[i],j)<<endl;
		}
	}
}