摘要：
G. GCD on a grid Not long ago, Egor learned about the Euclidean algorithm for finding the greatest common divisor of two numbers. The greatest common 阅读全文
摘要：
D. Colored Balls There are balls of $n$ different colors; the number of balls of the $i$-th color is $a_i$. The balls can be combined into groups. Eac 阅读全文