#20Ancient Roman Inscription

A Roman scribe is preparing inscriptions for important monuments across the empire. Instead of writing numbers using modern decimal notation, the scribe uses an ancient system of seven symbols.

Symbol → Value: I→ 1, V→ 5, X→ 10, L→ 50, C→ 100, D→ 500, M→ 1000

Roman inscriptions are written from the largest value to the smallest. For certain values, a subtractive form is used: 4 → IV 9 → IX 40 → XL 90 → XC 400 → CD 900 → CM

Given an integer num, help the Roman scribe convert it into its correct inscription.