PARSER_BEGIN(Assignment)
    class Assignment {
        public static void main(String[] args) throws ParseException, TokenMgrError
        {
            try {
                Assignment parser = new Assignment(System.in);
                parser.Start();
                System.out.println("PASS");
            } catch (ParseException e) {
                System.out.println("FAIL");
                System.err.println(e.currentToken.beginLine);
            }
        }
    }
PARSER_END(Assignment)

TOKEN : { <LEFT_PAREN: "(">}
TOKEN : { <RIGHT_PAREN: ")">}
TOKEN : { <NEWLINE: "\n">}
TOKEN : { <ANY: ~[]>}

void Start() : {}
{
    (ValidLine()<NEWLINE>)+<EOF>
}

// Single well-parenthesized string
void ValidLine() : {}
{
    <LEFT_PAREN>Parens()<RIGHT_PAREN>Parens()
}

// Recursion to allow arbitrary length of parentheses
void Parens() : {}
{
    <LEFT_PAREN>Parens()<RIGHT_PAREN>Parens() | Epsilon()
}

void Epsilon() : {}
{
    {} // Have to have some kind of body apparently
}