1. Seven children are standing in a circle: Anya, Borya, Vasya, Gena, Dasha, Eva, Zhena. Starting with one of the children, every third person clockwise leaves, and the counting continues until only one person remains. For example, if the counting starts with Anya (Anya - first), then Vasya leaves, in the next trio Gena is first, and Eva is third, so she leaves, then Borya leaves, and so on. From whom should the counting start so that Eva remains?
Answer. From Vasya.

Solution. Let's start counting from Anya. Gena will be left. Therefore, there needs to be a shift of 2 people, and we need to start from Vasya. Then the children leave in the following order: Dasha, Anya, Gena, Borya, Zhenya, Vasya.

Comment. Correct solution - 20 points. The solution is started, but the correct sequence of children leaving is not specified - 5 points. Only the correct answer without explanations - 1 point.