Hint Rewrite Znth_nthi using (auto; omega) : sublist.
Hint Resolve Zland_in_range.

Lemma sigma_1_eq:
forall s, sigma_1 s =
Int.xor
(Int.xor
(Int.or (Int.shl s (Int.repr 15))
(Int.shru s (Int.sub (Int.repr 32) (Int.repr 15))))
(Int.or (Int.shl s (Int.repr 13))
(Int.shru s (Int.sub (Int.repr 32) (Int.repr 13)))))
(Int.shru s (Int.repr 10)).