if(left.Length == 1) {

                        if (left.ToCharArray()[0] >= 65 && left.ToCharArray()[0] <= 90) {

                            // regular
                            if (right.Length == 2) {
                                if (right.ToCharArray()[0] >= 97 && right.ToCharArray()[0] <= 122 && right.ToCharArray()[1] >= 65 && right.ToCharArray()[1] <= 90) {
                                    type.Add("Regular");
                                }
                                else {
                                    if (right.ToCharArray()[1] >= 97 && right.ToCharArray()[1] <= 122 && right.ToCharArray()[0] >= 65 && right.ToCharArray()[0] <= 90) {
                                        type.Add("Regular");
                                    }
                                    else {
                                        type.Add("Libre de contexto");
                                    }
                                }
                            }
                            else {
                                if (right.Length == 1) {
                                    if (right.ToCharArray()[0] >= 97 && right.ToCharArray()[0] <= 122) {
                                        type.Add("Regular");
                                    }
                                    else {
                                        type.Add("Libre de contexto");
                                    }
                                }
                                else {
                                    type.Add("Libre de contexto");
                                }
                            }
                        }
                        else {
                            type.Add("Error");
                        }
                    }
                    else {
                        bool valid = false;
                        foreach (char letter in left.ToCharArray()) {
                            if (letter >= 65 && letter <= 90) {
                                valid = true;
                            }
                        }
                        if (valid) {
                            if (left.Length <= right.Length) {
                                type.Add("Sensitiva al contexto");
                            }
                            else {
                                type.Add("Irrestricta");
                            }
                        }
                        else {
                            type.Add("Error");
                        }
                    }

                }
                else {
                    type.Add("Error");
                }