19 soldiers have to cross the river. There is only one boat on the river. There can only be 4 soldiers on the boat at a time. How many times must they cross at least before all the soldiers can cross the river.
19名战士要过河，河上只有一条船，船上每次最多只能坐4名士兵，至少要渡多少次，才能使全体士兵过河．
<gadget id="calculator">19 - 4</gadget>
<output>15</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<result>6</result>