In a competition, among the participating students (1/7) won the first prize, (1/6) won the second prize, (1/3) won the third prize, and the rest won the commemorative prize. It is known that there are 56 students participating in this competition, and how many of them won the commemorative prize.
一次竞赛，参加学生中的(1/7)获一等奖，(1/6)获二等奖，(1/3)获得三等奖，其余获纪念奖．已知参加这次竞赛的学生为56人，获纪念奖的有多少人．
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

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

<gadget id="calculator">(1/7) + (1/6) + (1/3)</gadget>
<output>9/14 = around 0.642857</output>

<gadget id="calculator">1 - (9/14)</gadget>
<output>5/14 = around 0.357143</output>

<gadget id="calculator">56 * (5/14)</gadget>
<output>20</output>

<result>20</result>