12: (x - 1) => x - 1 belongs to U (12)
U (12) = {1,2,3,4,6,12, -1, -2, -3, -4, -6, -12}
x = 1 => 12: 0 (nonsense) x = 4 => 12: 3 = 4
x = -1 => 12: -2 = -6 x = -4 => 12: -5 (type)
x = 2 => 12: 12 = 1 x = 6 => 12: 5 (type)
x = -2 => 12: -3 = -4 x = -6 => 12: -7 (type)
x = 3 => 12: 2 = 6 x = 12 => 12:11 (type)
x = -3 => 12: -4 = -3 x = -12 => 12: -13
(species)
so x = {- 1,2, -2,3, -3} is satisfied
3 is the largest