Enter 49 in number-to-Roman mode. The largest available component is XL for 40, followed by IX for 9, so the canonical result is XLIX.

Compare IL with XLIX

In Roman-to-number mode, IL receives a provisional right-to-left value of 49 but fails the canonical comparison. RomanClear suggests XLIX; accepting it returns 49 with components XL and IX.

Reproduce the complete check

Run the decimal input first, record the emitted components and equation, then switch direction and enter the exact Roman output. The returned decimal value must match the starting integer. This two-way check demonstrates the selected profile without turning one example into a universal historical rule.