Among the 50 bunches of flowers, 16 bunches have rose flowers, 15 bunches have calla lilies, 21 bunches have white orchids, 7 bunches have both rose flowers and calla lilies, and 8 bunches have both calla lilies and white orchids, There are 10 bunches of roses and white orchids, and 5 bunches of flowers, including roses, calla lilies, and white orchids. Then, among the 50 bouquets of flowers, how many bouquets do not have the above three kinds of flowers?
在50束鲜花中，16束有月季花，15束有马蹄莲，21束有白兰花，有7束中既有月季花又有马蹄莲，有8束中既有马蹄莲又有白兰花，有10束中既有月季花又有白兰花，还有5束鲜花中，月季花、马蹄莲、白兰花都有．则50束鲜花中，上述三种花都没有的花束共有多少束
<gadget id="calculator">21 - 7 - 8 - 10</gadget>
<output>-4</output>

<gadget id="calculator">16 + 15 + (-4) + 5</gadget>
<output>32</output>

<gadget id="calculator">50 - 32</gadget>
<output>18</output>

<result>18</result>