What is the 50th item of the arithmetic sequence 3, 5, 7, 9...?
等差数列3、5、7、9…第50项是多少．
<gadget id="calculator">50 - 1</gadget>
<output>49</output>

<gadget id="calculator">49 * 2</gadget>
<output>98</output>

<gadget id="calculator">3 + 98</gadget>
<output>101</output>

<result>101</result>