73. The police officer turned at the sound of breaking glass and saw four teenagers running away from the broken storefront window. Five minutes later, they were at the police station. Andrey claimed that Viktor broke the glass, Viktor insisted that Sergey was to blame. Sergey assured that Viktor was lying, and Yury insisted that it wasn't him. From the further conversation, it became clear that only one of the boys was telling the truth. Who broke the glass?
73. Since only one of the boys told the truth, it is either - Viktor, or - Sergey (their statements contradict each other and cannot both be true or false at the same time). Therefore, all the others are lying. Yuri insisted that it was not him. If this is a lie, then Yuri is guilty.