total of 16 teams will be selected to participate in the final after the group stage of the World Cup. The final stage is carried out in a single elimination system, how many games are needed to determine the champion.
世界杯足球赛小组赛后共决出16支球队参加决赛．决赛阶段以单场淘汰制进行，共需要多少场才能决出冠军．
<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<gadget id="calculator">16 / 2 / 2</gadget>
<output>4</output>

<gadget id="calculator">16 / 2 / 2 / 2</gadget>
<output>2</output>

<gadget id="calculator">16 / 2 / 2 / 2 / 2</gadget>
<output>1</output>

<gadget id="calculator">8 + 4 + 2 + 1</gadget>
<output>15</output>

<result>15</result>