diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index f2bb0d8..cac6eb6 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,5 +1,9 @@
 String integerToRoman(int number) {
   const conversionRules = [
+    (1000, 'M'),
+    (900, 'CM'),
+    (500, 'D'),
+    (400, 'CD'),
     (100, 'C'),
     (90, 'XC'),
     (50, 'L'),