Set: pp::colors
  Set: pp::unicode
  Imported 'Int'
  Assumed: f
  Proved: T1
  Proved: T2
theorem T1 (a b c : ℤ) (H1 : a = b) (H2 : a = c) : f (f a a) b = f (f b c) a :=
    congr (congr (refl f) (congr (congr (refl f) H1) H2)) (symm H1)
theorem T2 (a b c : ℤ) (H1 : a = b) (H2 : a = c) : f (f a c) = f (f b a) :=
    congr (refl f) (congr (congr (refl f) H1) (symm H2))