let eq1'' := eq1'.1
α : Type
inst✝ : DecidableEq α
start : List (α × Bool)
letter : α × Bool
reduced_start : Reduced start
nilP : ¬start = []
L' : List (α × Bool)
step : Step (start :+ letter) L'
x : α
b : Bool
L₁ L₂ : List (α × Bool)
eqs : start :+ letter = L₁ ++ (x, b) :: (x, !b) :: L₂ ∧ L' = L₁ ++ L₂
cancP : ¬List.getLast start nilP = letter⁻¹
endP : ¬L₂ = []
eq1 : List.concat start letter = List.concat (L₁ ++ (x, b) :: (x, !b) :: List.dropLast L₂) (List.getLast L₂ endP)
eq1' : start = L₁ ++ (x, b) :: (x, !b) :: List.dropLast L₂ ∧ letter = List.getLast L₂ endP :=
  List.of_concat_eq_concat eq1
⊢ False
α : Type
inst✝ : DecidableEq α
start : List (α × Bool)
letter : α × Bool
reduced_start : Reduced start
nilP : ¬start = []
L' : List (α × Bool)
step : Step (start :+ letter) L'
x : α
b : Bool
L₁ L₂ : List (α × Bool)
eqs : start :+ letter = L₁ ++ (x, b) :: (x, !b) :: L₂ ∧ L' = L₁ ++ L₂
cancP : ¬List.getLast start nilP = letter⁻¹
endP : ¬L₂ = []
eq1 : List.concat start letter = List.concat (L₁ ++ (x, b) :: (x, !b) :: List.dropLast L₂) (List.getLast L₂ endP)
eq1' : start = L₁ ++ (x, b) :: (x, !b) :: List.dropLast L₂ ∧ letter = List.getLast L₂ endP :=
  List.of_concat_eq_concat eq1
eq1'' : start = L₁ ++ (x, b) :: (x, !b) :: List.dropLast L₂ := eq1'.left
⊢ False