def matrixMul(firstMatrix, secondMatrix):
    """
    Return the result of matrix multiplication of firstMatrix and secondMatrix
    """
    ret = []

    for i in range(0, len(firstMatrix)):
        ret.append([])

        for j in range(0, len(secondMatrix[i])):
            ret[i].append(0)

            for k in range(0, len(firstMatrix[i])):
                ret[i][j] += firstMatrix[i][k] * secondMatrix[k][j]

    return ret