Roman Numeral Converter

Roman numerals use 7 symbols: I (1), V (5), X (10), L (50), C (100), D (500), M (1000). Numbers are formed by combining symbols from largest to smallest, left to right. Subtractive notation: when a smaller value precedes a larger one, it is subtracted — IV = 4 (5-1), IX = 9 (10-1), XL = 40, XC = 90, CD = 400, CM = 900. This subtractive convention was standardized in medieval Europe.

Standard Roman numerals (without overlines or parentheses) go up to MMMCMXCIX (3999). The Romans used an overline (vinculum) above a numeral to multiply it by 1000, extending the range. Modern applications typically limit to 3999 for simplicity. Technically, clock faces often use IIII instead of IV for 4, as it looks more balanced.

Roman numerals appear on clock faces, movie sequels and series (Star Wars Episode IV), book chapters, Super Bowl numbering, Olympic Games, architectural inscriptions and cornerstones (dates), page numbering in book front matter, legal code sections, and formal outlines. They are also used in astronomy (Galilean moons: Io is Jupiter I) and music theory (chord numerals).

3999, written as MMMCMXCIX. To represent 4000 and above, the Roman system historically used a bar over a numeral (vinculum) to multiply by 1,000: V̄ = 5,000, X̄ = 10,000, L̄ = 50,000, C̄ = 100,000, D̄ = 500,000, M̄ = 1,000,000. Some uses also employed parentheses: (V) = 5,000. These extensions are not commonly used in modern contexts.

Scan left to right. If the current value is less than the next value, subtract it (subtractive rule); otherwise add it. In Python: values = {I:1, V:5, X:10, L:50, C:100, D:500, M:1000}; result = 0; for i in range(len(s)): result += (-1 if i+1 < len(s) and values[s[i]] < values[s[i+1]] else 1) * values[s[i]]. The same logic works in any language.