CREATE OR REPLACE FUNCTION f_words_usd(p_number NUMERIC)
RETURNS VARCHAR AS $$
DECLARE
    l_str TEXT[] := ARRAY['', 'thousand', 'million', 'billion', 'trillion', 'quadrillion', 'quintillion', 'sextillion', 'septillion', 'octillion', 'nonillion', 'decillion', 'undecillion', 'duodecillion'];
    units TEXT[] := ARRAY['', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine'];
    teens TEXT[] := ARRAY['eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen'];
    tens TEXT[] := ARRAY['', 'ten', 'twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 'eighty', 'ninety'];

    l_num VARCHAR := TRUNC(p_number)::VARCHAR;
    l_return TEXT := '';
    l_decimal NUMERIC;
    l_return_decimal TEXT := '';
    i INTEGER;
    segment_len INTEGER;
    segment INT;
    segment_text TEXT;
    
    -- Helper function to convert a three-digit segment to words
    FUNCTION three_digit_to_words(segment INT) RETURNS TEXT AS $$
    DECLARE
        hundred_part INT;
        ten_part INT;
        unit_part INT;
        segment_words TEXT := '';
    BEGIN
        hundred_part := segment / 100;
        ten_part := (segment % 100) / 10;
        unit_part := segment % 10;

        IF hundred_part > 0 THEN
            segment_words := segment_words || units[hundred_part + 1] || ' hundred ';
        END IF;

        IF ten_part = 1 AND unit_part > 0 THEN
            segment_words := segment_words || teens[unit_part] || ' ';
        ELSE
            IF ten_part > 0 THEN
                segment_words := segment_words || tens[ten_part + 1] || ' ';
            END IF;
            IF unit_part > 0 THEN
                segment_words := segment_words || units[unit_part + 1] || ' ';
            END IF;
        END IF;

        RETURN segment_words;
    END;
    $$ LANGUAGE plpgsql;
    
BEGIN
    -- Calculate decimal part
    l_decimal := p_number - TRUNC(p_number);

    FOR i IN 1 .. array_length(l_str, 1) LOOP
        EXIT WHEN l_num IS NULL OR l_num = '';

        segment_len := GREATEST(LENGTH(l_num) - 2, 1);
        segment := SUBSTR(l_num, segment_len, 3)::INT;

        IF segment <> 0 THEN
            segment_text := three_digit_to_words(segment);
            l_return := segment_text || l_str[i] || ' ' || l_return;
        END IF;

        l_num := LEFT(l_num, GREATEST(LENGTH(l_num) - 3, 0));
    END LOOP;

    IF l_return IS NOT NULL THEN
        l_return := l_return || 'US Dollar ';
    END IF;

    -- Handle decimal part
    IF l_decimal != 0 THEN
        l_decimal := l_decimal * 100;
        segment_text := three_digit_to_words(l_decimal::INT);
        l_return := l_return || 'and ' || segment_text || 'Cents ';
    END IF;

    IF l_return IS NOT NULL THEN
        l_return := l_return || 'Only';
    END IF;

    RETURN l_return;
END;
$$ LANGUAGE plpgsql;