四方定理描述： 在数论中有一个著名的“四方定理”，它的含义是： 所有自然数至多只要用四个数的平方和就可以表示。 要求： 该题是一个定理，我们不是去证明它，而是要求同学们编程 序来验证该定理的正确性。 输入： 用户从键盘任意输入一个自然数。 输出： 给出满足四方定理中的至多四个自然数。-Quartet theorem Descr iption : Number Theory in a famous "Quartet Theorem," meaning it is : all natural number can use up to four the number of square and can be expressed. Requirements : The title is a theorem, we will prove it, but to require the students programmed to verify the correctness of the theorem. Input : arbitrary user input from the keyboard to a natural number. Output : the Quartet is to meet the theorem up to four natural number.