# Natural Numbers

*English translation by SOTA – AI Community of the Russian original. Organisers who would like this translation removed can email sota.ai.community@gmail.com.*

All-Russian School Olympiad in Informatics 2025–2026, Regional Stage, Grades 9–11<br>
“Artificial Intelligence” profile, Tour 1, 17 January 2026<br>
Task A

**Points for the task:** 50<br>
**Answer submission format:** entering the answer<br>
**Number of attempts:** 10<br>
**Submission that counts:** the last one

## Statement

One hundred natural numbers were written in a row, one after another. The second number was equal to 1, and each number, starting from the third, is equal to the sum of all the numbers written before it. Then the first number was erased. It turned out that one of the remaining numbers is equal to 123456123456123456. What could the erased number have been?

## Output format

As your answer, output all suitable values **in ascending order**, separated by spaces.

## Scoring

An exact match of the answer: 50 points.

Test results are **not available** during the tour.