#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <sstream>
#include <algorithm>
#include <stack>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */
    vector<string> operations;
    stack<pair<int, string>> undo;
    int numOfOps;
    cin >> numOfOps;
    cin.ignore();
    string str = "";
    for (int i = 0; i < numOfOps; ++i) {
        string op;
        getline(cin, op);
        int code;
        string arg;
        stringstream ss(op);
        ss >> code >> arg;
        switch (code) {
            case 1:
                str += arg;
                undo.push({1, arg});
                break;
            case 2:
                undo.push({2, str.substr(str.size() - stoi(arg))});
                str.erase(str.size() - stoi(arg));
                break;
            case 3:
                cout << str[stoi(arg) - 1] << endl;
                break;
            case 4:
                auto [lastOp, lastItem] = undo.top();
                switch (lastOp) {
                    case 1:
                        str.erase(str.size() - lastItem.size());
                        break;
                    case 2:
                        str += lastItem;
                        break;
                }
                undo.pop();
                break;
        }
    }
    return 0;
}