r= x^20 - x^18 + x^16 - x^14 + x^12 - x^10 + x^8 - x^6 + x^4 - x^2 + 1 q= (x^26 - 2*x^24 + x^22 + x^4 + 2*x^2 + 1) / 4 P= x^13 - 2*x^12 + x^11 + x^2 - x + 1 v= x^2