It’s universally acknowledged that there’re innumerable trees in the campus of HUST. One day, zjh is wandering in the campus,and he finds a tree with n monkeys on it, and he labels the monkeys from 1 to n. A triple of monkeys is called happy if and only if the absolute value of the difference of the distance from c to a the distance from c to b holds the same parity(奇偶性) as n. Now zjh wants to know how many triples of monkeys are happy.
It’s universally acknowledged that there’re innumerable trees in the campus of HUST. One day, zjh is wandering in the campus,and he finds a tree with n monkeys on it, and he labels the monkeys from 1 to n. A triple of monkeys (a,b,c) is called happy if and only if the absolute value of the difference of the distance from c to a the distance from c to b holds the same parity(奇偶性) as n. Now zjh wants to know how many triples of monkeys are happy.
（图片来源网络，侵删）
