Students in a certain class take an exam and their grades are divided into four grades: Excellent, Good, Pass, and Fail. It is known that (1/2) of the students in the class are excellent, (1/3) of the students are good, and (1/7) of the students are passing. If the number of students in the class does not exceed 50, how many failed students are there?
某班学生参加一次考试，成绩分为优、良、及格、不及格四等．已知该班有(1/2)的学生得优，有(1/3)的学生得良，有(1/7)的学生及格．如该班学生人数不超过50人，则不及格的学生有多少人．
<gadget id="calculator">2 * 3 * 7</gadget>
<output>42</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 - (1/2) - (1/3) - (1/7)</gadget>
<output>1/42 = around 0.02381</output>

<gadget id="calculator">42 * (1/42)</gadget>
<output>1</output>

<result>1</result>