2. A black and white chocolate bar consists of individual pieces forming $n$ horizontal and $m$ vertical rows, arranged in a checkerboard pattern. Yan ate all the black pieces, and Maxim ate all the white pieces. What is $m+n$, if it is known that Yan ate $8 \frac{1}{3} \%$ more pieces than Maxim.
Solution. The number of black and white segments can only differ by 1. Therefore, Yan ate 1 segment more than Maksim. If 1 segment is 8 $\frac{1}{3} \%$, then Maksim ate 12 segments, Yan ate 13 segments, and together they ate 25 segments. This means the chocolate bar was $5 \times 5$.

Answer: 10.

Criteria: 14 points for a justified correct solution. 12 points for a correct solution with an arithmetic error. 6 points for stating that Yan ate 1 segment more than Maksim. 2 points for the correct answer only. (Do not deduct points for the answer $26-25+1$.)