have md : d % (t + 1) = d := mod_eq_of_lt (succ_le_succ hd)
c t d a b : ℕ
hc : c ≤ t
hd : d ≤ t
ht : (t + 1) * a + c = (t + 1) * b + d
mc : c % (t + 1) = c
⊢ a = b ∧ c = d
c t d a b : ℕ
hc : c ≤ t
hd : d ≤ t
ht : (t + 1) * a + c = (t + 1) * b + d
mc : c % (t + 1) = c
md : d % (t + 1) = d
⊢ a = b ∧ c = d