7.4. A number is called good if any two adjacent digits in its notation differ by at least 5. Vera wrote a good number, and then replaced identical digits with identical letters, and different digits with different letters. Could she have ended up with the word NOVOSIBIRSK?
Answer: No.

Solution: Suppose this could have happened. Let's call the digits $0,1,2,3,4$ small digits, and the remaining digits large. Note that under the described replacement, two small digits cannot stand next to each other, just as two large digits cannot stand next to each other, because the difference between any two small (and any two large) digits does not exceed 4. Therefore, small and large digits must alternate. Notice that between two C letters, there are 4 letters, which means one C letter replaces a small digit, and the other a large digit, but they represent the same digit, which is impossible.

Criteria: Only the answer - 0 points. An unexplained observation that small and large digits alternate - no points deducted. The idea of alternating large and small digits without further progress - 2 points.