#include <bits/stdc++.h>
using namespace std;
 
 
int main() {
    string s = "";
    int cas;
    cin >> cas;
    vector<string> prev;
    for(int i = 0; i < cas; i++){
        string t, r;
        cin >> t; 
        if(t != "4") cin >> r;
 
        if(t == "1"){
            prev.push_back(s);
            s += r;
        }
        else if( t == "2"){
            prev.push_back(s);
            s.erase(s.end() - stoi(r), s.end());
        }
        else if(t == "3"){ cout << s[stoi(r)-1] << endl; }
        else {
            s = prev.back();
            prev.pop_back();
        }
    }
    return 0;
}

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OAoxIGFiYwozIDMKMiAzCjEgeHkKMyAyCjQKNAozIDE=

8
1 abc
3 3
2 3
1 xy
3 2
4
4
3 1