Constant KOALABEAR_S_BOX_DEGREE 

pub const KOALABEAR_S_BOX_DEGREE: u64 = 3;

S-box degree for KoalaBear Poseidon1.

Since p - 1 = 127 * 2^24, both 127 and 2 are the only prime factors of p - 1.

So gcd(3, p - 1) = 1, and x^3 is the smallest valid permutation polynomial.