class SEditor {
    private _stacks: string[];
    private _stacks_cursor: number;
    private get s() { return this._stacks[this._stacks_cursor] }
    
    /**
     * Simple editor with a [stacks] stored string state after every steps,
     * Can undo & redo with [cursor], [redo] will be overriden by [append]&[delete]
     */
    
    constructor(s: string, private ws: WriteStream) {
        this._stacks = [s]
        this._stacks_cursor = 0
    }

    public _append(w: string): void {
        this._stacks.splice(this._stacks_cursor + 1)
        this._stacks.push(this.s + w)
        this._stacks_cursor++
    }
    public _delete(k: number): void {
        this._stacks.splice(this._stacks_cursor + 1)
        this._stacks.push(this.s.substring(0, this.s.length - k))
        this._stacks_cursor++
    }
    public _print(k: number): void { this.ws.write(this.s[k - 1] + '\n'); }
    public _undo(): void { this._move_cursor(-1) }
    public _redo(): void { this._move_cursor(+1) }

    private _move_cursor(steps: number): void {
        this._stacks_cursor = Math.max(0, Math.min(this._stacks_cursor + steps, this._stacks.length - 1));
    }
}
function main() {
    const ws: WriteStream = createWriteStream(process.env['OUTPUT_PATH']);
    const q: number = parseInt(readLine().trim(), 10);
    const s = new SEditor('', ws)

    for (let i = 0; i < q; i++) {
        let [t, w] = readLine().split(' ');
        switch (t) {
            case '1': s._append(w); break;
            case '2': s._delete(parseInt(w, 10)); break;
            case '3': s._print(parseInt(w, 10)); break;
            case '4': s._undo(); break;
        }
    }
}