A mathematics competition with first, second and third prizes. Many students won prizes, among which the number of first prizes accounted for (1/7) of the total number of participants in the competition, the number of second prizes accounted for (1/3) of the total number of participants in the competition, and the number of third prizes accounted for 1/7 of the total number of participants. (1/2) of the total number of contestants. At least how many students participate in the competition.
一次数学竞赛，设有一、二、三等奖．有很多同学获奖，其中获得一等奖的人数占参加竞赛总人数的(1/7)，获得二等奖的人数占参加竞赛总人数的(1/3)，获得三等奖的人数占参加竞赛总人数的(1/2)．至少有多少名同学参加竞赛．
<gadget id="calculator">7 * 3 * 2</gadget>
<output>42</output>

<result>42</result>