Two students, Zhang Jun and Liu Wei, want to buy a football together. Zhang Jun has 13.5 yuan, Liu Wei has 16.8 yuan, and the price of a football is 36.5 yuan. How much money do they need to buy this football?
张军和刘伟两个同学要合买一个足球．张军有13.5元，刘伟有16.8元，一个足球的价钱是36.5元，他们要买这个足球还差多少元？
<gadget id="calculator">36.5 - 13.5 - 16.8</gadget>
<output>6.2</output>

<result>6.2</result>