摘要：7720: RGB Coloring 题目描述 Takahashi has a tower which is divided into N layers. Initially, all the layers are uncolored. Takahashi is going to paint som 阅读全文

摘要：We have a sandglass consisting of two bulbs, bulb A and bulb B. These bulbs contain some amount of sand. When we put the sandglass, either bulb A or B 阅读全文