Create a function that returns the number of (real) solutions of ax^4+bx^2+c=0. The function will take three arguments: a as the coefficient of x^4, b as the coefficient of x^2, and c as the constant term.

Examples

quartic_equation(1, -5, 4) ➞ 4

quartic_equation(4, 3, -1) ➞ 2

quartic_equation(1, 10, 9) ➞ 0

Notes

Hint: Try substitution t=x^2.