In the "Good Books for Everyone" activity held by the school, the fourth grade students donated a total of 1620 books, which is 508 books less than twice the number of books donated by the second graders. How many books did the second graders donate?
在学校举行的"好书大家读"的活动中，四年级同学共捐书1620本，比二年级捐的本数的2倍少508本．二年级同学共捐书多少本？
<gadget id="calculator">1_620 + 508</gadget>
<output>2_128</output>

<gadget id="calculator">2_128 / 2</gadget>
<output>1_064</output>

<result>1_064</result>