Counting Rhombi

题意翻译

求满足以下条件的菱形个数： - 面积为整数。 - 顶点为整点（即 $x,y$ 坐标都是整数）。 - 顶点在矩形 $(0,0),(w,0),(w,h),(0,h)$ 的边上或内部（即 $0\leq x\leq w$，$0\leq y\leq h$）。 - 对角线平行于轴线。

题目描述

You have two positive integers $ w $ and $ h $ . Your task is to count the number of rhombi which have the following properties: - Have positive area. - With vertices at integer points. - All vertices of the rhombi are located inside or on the border of the rectangle with vertices at points $ (0,0) $ , $ (w,0) $ , $ (w,h) $ , $ (0,h) $ . In other words, for all vertices $ (x_{i},y_{i}) $ of the rhombus the following conditions should fulfill: $ 0<=x_{i}<=w $ and $ 0<=y_{i}<=h $ . - Its diagonals are parallel to the axis. Count the number of such rhombi. Let us remind you that a rhombus is a quadrilateral whose four sides all have the same length.

输入输出格式

输入格式

The first line contains two integers $ w $ and $ h $ $ (1<=w,h<=4000) $ — the rectangle's sizes.

输出格式

Print a single number — the number of sought rhombi. Please do not use the %lld specifier to read or write 64-bit integers in С++. It is preferred to use cin, cout streams or the %I64d specifier.

输入输出样例

输入样例 #1

2 2

输出样例 #1

1

输入样例 #2

1 2

输出样例 #2

0

说明

In the first example there exists only one such rhombus. Its vertices are located at points $ (1,0) $ , $ (2,1) $ , $ (1,2) $ , $ (0,1) $ .