A monkey found peaches on a peach tree. It jumped on the tree and ate more than half of the peaches on the first day, jumped on the tree on the second day and ate more than half of the remaining peaches, and on the third day As soon as he jumped on the tree, he was captured alive by the owner of the peach tree. The owner was so angry that he picked all the remaining 12 peaches. How many peaches were there in this peach tree?
一只猴子发现了桃树上的桃子，它第一天跳到树上就偷吃了桃子总数的一半多半个，第二天又跳上树偷吃了剩余桃子的一半多半个，第三天刚跳上树就被桃树主人活捉了，气得主人把剩下的12个桃子全摘走了，这棵桃树上原有多少个桃子？
<gadget id="calculator">12 + 0.5</gadget>
<output>12.5</output>

<gadget id="calculator">12.5 * 2</gadget>
<output>25</output>

<gadget id="calculator">25 + 0.5</gadget>
<output>25.5</output>

<gadget id="calculator">25.5 * 2</gadget>
<output>51</output>

<result>51</result>