exact sterbenz hfc hfa hac hle
case inl
n a b c : ℕ
npos : 0 < n
hac : a ≤ c
hcb : c ≤ b
hfa : trunc n a = a
hfb : trunc n b = b
hfc : trunc n c = c
hf : trunc n (b - a) = b - a
hle : c ≤ 2 * a
⊢ trunc n (c - a) = c - a
no goals