Description: You, a 6th grade student, come to school at night to look for something you forgot. Something strange is happening at school, and you can't get to your classroom by simply climbing the stairs. First, explore the first floor and memorize what is where. After that, explore each floor, and if there is nothing unusual, go up the stairs, and if there is anything unusual, go down the stairs. Things that were there are gone, their shapes have changed, and there are many abnormalities. If you make it to the 6th floor, you will find your destination, Class 6, and your forgotten items. What did you forget and why did you forget it? It may become clear by looking at all the abnormalities.