During the Long March, 76 commanders and fighters of a Red Army unit had to cross the river by boat. There was only one wooden boat (without a boatman) at the ferry crossing. If all the troops were to be sent to the other side of the river, they would use this wooden boat to cross the river. At least how many times.
长征时期，一支红军部队的76位指战员要坐船过河，渡口处只有一条可载16人的木船(无船工)，那么要将这支部队全部送到河对岸，则用这条木船渡河至少多少次．
<gadget id="calculator">76 - 1</gadget>
<output>75</output>

<gadget id="calculator">16 - 1</gadget>
<output>15</output>

<gadget id="calculator">75 / 15</gadget>
<output>5</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<result>9</result>