child blows soap bubbles once every minute, exactly 100 bubbles are blown each time. After the soap bubbles are blown out, half of them burst after 1 minute; half burst again after 2 minutes; When the child blows for the 100th time, how many soap bubbles are left unbroken?
小朋友每分钟吹一次肥皂泡，每次恰好吹出100个．肥皂泡吹出以后，经过1分钟，有一半破了；经过2分钟又破了一半；到3分钟时全破了．这个小朋友吹完第100次时，没有破的肥皂泡共有多少个．
<gadget id="calculator">100 / 2</gadget>
<output>50</output>

<gadget id="calculator">100 / 2 / 2</gadget>
<output>25</output>

<gadget id="calculator">100 + 50 + 25</gadget>
<output>175</output>

<result>175</result>