48 students participated in the party. The first boy who came to the meeting shook hands with all the girls. The second boy who came to the meeting was only one girl away from shaking hands, and the third boy who came to the meeting was only two girls away from shaking hands... The last boy who came to the meeting shook hands with 9 girls. How many girls are there among the 48 students?
48名学生参加聚会，第一个到会的男生和全部女生握手，第二个到会的男生只差一名女生没握过手，第三个到会的男生只差2名女生没握过手…最后一个到会的男生同9名女生握过手，这48名学生中共有多少名女生．
<gadget id="calculator">48 + 8</gadget>
<output>56</output>

<gadget id="calculator">56 / 2</gadget>
<output>28</output>

<result>28</result>