absurd h
m₁ n₁ m₂ n₂ : Nat
h₁ : m₁ ≤ n₁
h₂ : m₂ ≤ n₂
h : n₁.tri + m₁ = n₂.tri + m₂
hgt : ¬n₁ ≤ n₂
x✝ : Decidable (n₁ ≥ n₂)
⊢ n₁ = n₂
m₁ n₁ m₂ n₂ : Nat
h₁ : m₁ ≤ n₁
h₂ : m₂ ≤ n₂
h : n₁.tri + m₁ = n₂.tri + m₂
hgt : ¬n₁ ≤ n₂
x✝ : Decidable (n₁ ≥ n₂)
⊢ ¬n₁.tri + m₁ = n₂.tri + m₂