School algebra

Trinomial a x + b y + c of two variables $x$ and $y$ is uniquely determined by the constant term $c$ and the coefficients $a$ and $b$. Write a program that, given $a$, $b$ and $c$, displays the corresponding trinomial recorded using algebraic rules:

• the coefficient of the term containing the variable is omitted if it is equal to one;

• a term whose coefficient is equal to zero is omitted;

• the "+" sign is omitted if it is followed by a negative coefficient;

• the "+" sign is omitted if it is at the beginning (the so-called unary plus);

• the multiplication sign between the coefficient and the variable is omitted.

At the same time, it is not allowed to swap terms.