Roman Numerals
Numbers to Roman numerals and back, with the malformed ones rejected.
Result
Good to know
- Which way it converts is decided by what you type: digits become a numeral, letters become a number.
- A numeral is checked by converting the result back: if it does not come out identical, the input was not properly formed — which is how IIII and IC are caught.
- Subtraction is limited to the usual six pairs, so 9 is IX and 40 is XL, never VIIII or XXXX.
- Everything happens in your browser. Nothing you type is sent to the server or stored anywhere.
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