There are 60 cards placed from left to right. Xiao Rao writes 1, 2, 1, 2, 1, 2, 1, 2, 1, ... on the cards in order from left to right; Write 1, 2, 3, 1, 2, 3, 1, 2,... on the cards in order; Xiao Song writes the two numbers written by Xiao Rao and Xiao Lin on the back of each card. difference (big reduction), then what is the sum of the 60 numbers written by Xiao Song.
从左到右放有60张卡片，小饶按从左到右的顺序在卡片上依次写上1，2，1，2，1，2，1，2，1，…；小林从右到左按顺序依次在卡片上写上1，2，3，1，2，3，1，2，…；小宋在每张卡片的背面分别写上小饶与小林在此卡片上所写两数的差(大减小)，那么小宋写的60个数的和是多少．
<gadget id="calculator">60 / 6</gadget>
<output>10</output>

<gadget id="calculator">10 * 5</gadget>
<output>50</output>

<result>50</result>