Xiao Gang did shuttlecock kicking practice, the first time he kicked 57 times, and the second time he kicked 66 times. If he wants to achieve an average score of 70 three times, how many times should he kick at least for the third time.
小刚做踢毽子练习，第一次踢了57下，第二次踢了66下．他要想三次平均成绩达到70下，第三次至少要踢多少下．
<gadget id="calculator">70 * 3</gadget>
<output>210</output>

<gadget id="calculator">57 + 66</gadget>
<output>123</output>

<gadget id="calculator">210 - 123</gadget>
<output>87</output>

<result>87</result>