def cp_key(c, ring):
 return (lbp_key(lbp(c[0], ring.zero, Num(c[2]))), lbp_key(lbp(c[3], ring.zero, Num(c[5]))))

def cp_key ( c , ring ) : return ( lbp_key ( lbp ( c [ 0 ] , ring . zero , Num ( c [ 2 ] ) ) ) , lbp_key ( lbp ( c [ 3 ] , ring . zero , Num ( c [ 5 ] ) ) ) )
key for comparing critical pairs .