NUMERAL_MAPPINGS = (
    (1000, 'M'), (900, 'CM'),
    (500, 'D'), (400, 'CD'),
    (100, 'C'), (90, 'XC'),
    (50, 'L'), (40, 'XL'),
    (10, 'X'), (9, 'IX'),
    (5, 'V'), (4, 'IV'),
    (1, 'I')
)


def roman(number):
    result = ''
    for arabic_num, roman_num in NUMERAL_MAPPINGS:
        while number >= arabic_num:
            result += roman_num
            number -= arabic_num
    return result