Problem

Source: Lusophon 2016 CPLP P3

Tags: polynomial, algebra, Integer Polynomial, Sum, roots of the equation



Suppose a real number $a$ is a root of a polynomial with integer coefficients $P(x)=a_nx^n+a_{n-1}x^{n-1}+...+a_1x+a_0$. Let $G=|a_n|+|a_{n-1}|+...+|a_1|+|a_0|$. We say that $G$ is a gingado of $a$. For example, as $2$ is root of $P(x)=x^2-x-2$, $G=|1|+|-1|+|-2|=4$, we say that $4$ is a gingado of $2$. What is the fourth largest real number $a$ such that $3$ is a gingado of $a$?