摘要：
Let's call an array of non negative integers a1,a2,…,an a k extension for some non negative integer k if for all possible pairs of indices 1≤i,j≤n the 阅读全文
摘要：
n boys and m girls came to the party. Each boy presented each girl some integer number of sweets (possibly zero). All boys are numbered with integers 阅读全文
摘要：
A. A pile of stones Vasya has a pile, that consists of some number of stones. n times he either took one stone from the pile or added one stone to the 阅读全文