#55451: c++
#include <bits/stdc++.h>
using namespace std;
int main(){
int t,move;
cin>>t;
stack <int> s;
while(t--){
cin>>move;
if(move==3){if(s.empty())continue;s.pop();}
else if(move==2){if(s.empty()){cout<<"-1"<<endl;continue;}cout<<s.top()<<endl;}
else if(move==1){cin>>move;s.push(move);}
}
return 0;
}