**KANGAROO**upon the following rules:

1. Similar letters are replaced by the same digit

2. The resulting 8-digit number must be divisible by 11.

3. Maxim had to choose the maximal qualifying number, Minerva - the minimal.

Comparing their correct answers they've found out that a certain letter in the word **KANGAROO** was replaced by the same digit in their independent answers.

Specify **WHAT** letter and explain **WHY.**