Number of rectangles

In a computer science class, some less diligent students came up with a game. They drew a rectangle on grid paper, with its sides aligned along the grid lines. Their challenge was to count all possible rectangles that could be formed using the grid lines within the drawn rectangle. Tired of this activity, their teacher, Albert Ververovich, tasked them with writing a program to automate this calculation.

Input

Two natural numbers separated by a space, each not exceeding 10,000, representing the dimensions of the rectangle.

Output

A single number representing the total number of rectangles that can be formed.

Examples