Create number to Roman mapping lists [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1] to ['M', 'CM', 'D', 'CD', 'C', 'XC', 'L', 'XL', 'X', 'IX', 'V', 'IV', 'I'].
Recursively call the algorithm to convert the remainder of the input number (after subtracting the closest match multiplied by the number of repeats).