The three brothers collect stamps, the stamp of the second collection is three times as much as that of the boss, and the stamp of the third collection is half of that of the boss and one less. It is known that the three people have a total of 180 stamps, how many stamps are there in the third episode?
兄弟三人集邮，老二集的邮票是老大集的邮票的3倍还多一枚，老三集的邮票是老大的一半还少一枚．已知三人共有邮票180枚，则老三集的邮票有多少枚．
<gadget id="calculator">180 - 1</gadget>
<output>179</output>

<gadget id="calculator">1 + 179</gadget>
<output>180</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 + 3 + (1/2)</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">180 / (9/2)</gadget>
<output>40</output>

<gadget id="calculator">40 * (1/2)</gadget>
<output>20</output>

<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<result>19</result>