int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int q=0;
    cin >> q;
    string s ="";
    stack<string> v;
    v.push(s);
    for(int i=0; i<q; i++){
        int op = 0;string ss;
        cin >> op;
        if(op != 4)cin >> ss;
        switch (op) {
            case 1:
               s+=ss;
               v.push(s);
               break;
            case 2:
                s = s.substr(0, s.length() - stoi(ss));
                v.push(s);
                break;
             case 3:
                cout << v.top()[stoi(ss)-1]<<endl;
                break;
            case 4:
                v.pop();
                s = v.top();
                break;
        }
    }
    
    return 0;
}