I am at a loss on this one. Many of the test cases are failing, yet my output when I run locally matches the expected output perfectly. I get 'wrong answer'. If anyone has a clue what it could be let me know. My code:

private static final Scanner scanner = new Scanner(System.in);
private static Stack<String> state = new Stack<>();

public static void main(String[] args) throws IOException {
    state.push("");
    while (scanner.hasNext()) {
        String command = scanner.nextLine();
        int op = command.charAt(0) - '0';
        switch (op) {
            case 1:
                String toAppend = command.substring(2);
                state.push(append(state.peek(), toAppend));
                break;
            case 2:
                int charsToDelete = Integer.parseInt(command.substring(2));
                state.push(delete(state.peek(), charsToDelete));
                break;
            case 3:
                int charToPrint = Integer.parseInt(command.substring(2));
                System.out.println(state.peek().charAt(charToPrint - 1));
                break;
            case 4:
                state.pop();
                break;
        }

    }
}

private static String append(String text, String toAppend) {
    return text + toAppend;
}

private static String delete(String text, int charsToDelete) {
    return text.substring(0, text.length() - charsToDelete);
}