$//$ This function returns the smallest non$-$negative integral root of a polynomial $($as specified by a list of coefficients and degree$)$ that is no larger than xmax. Return $-1$ if there is no roots within the range.

$//$To be specific: for each integer $0<=$i $<=$ degree, listCoeffs$[$d$]=$ the coefficient of the degree d term. For example,

int ECFindRoot$($int $*$listCoeffs$,$ int degree, int xmax$)$

$\{$

$//$ listCoeffs: pointer to the array of integers as the coefficients of a polynomial; listCoeffs$[0]$ is the constant term and so on

$//$ degree: highest degree term. That is$,$ the number of coefficients in the array $=$ degree$+1$

$//$ xmax: the largest value of root to search

$//$ your code here