用减奇数次数的方法，求一个数的近似平方根，这个平方根是一个整数。如求17的平方根，可以用17相继减去奇数1、3、5、7、…，当结果为 负数时停止，即：



17-1-3-5-7-9＜0



可以看出，17在减去5次奇数后结果变为负数，可以近似认为17的平方根在4与5之间，计算NUM的平方根，如果NUM=17，则ANS中保存结果4。

-Save odd-frequency method, find a number of approximate square root of the square root is an integer. Such as for the square root of 17, 17 can be used successively subtracting the odd-numbered 1,3,5,7, ..., and stopped when the result is negative, i.e.: 17-1-3-5-7-9 < 0 As can be seen, 17 minus 5 odd result becomes negative, can be approximated by the square root of 17 is between 4 and 5 to calculate the square root of the NUM, if num = 17, then save the results of the ANS.