# Sparse Matrix Multiplication

Given two sparse integer matrices `A` and `B`. Return the result of `AB`.

Review the rules of multiple two matrices here

Below is a graphical demonstration of matrix multiplication:

A "sparse" matrix is a matrix where most entries are zero. You may assume that the number of columns in `A` is equal to that of the number of rows in `B`.

### Input

• `a`: an integer matrix.
• `b`: an integer matrix.

### Output

An integer matrix represent the product of the above matrices.

### Examples

#### Example 1:

Input:

``````1a = [[1, 0, 3], [0, 1, 2]]
2b = [[0, 1], [1, 3], [0, 0]]``````

Output: `[[0, 1], [1, 3]]`

Explanation:

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``````1  >>> a = [1, 2, 3]
2  >>> a[-1]
3  3``````