Lemma while_loop_post_incremental_fst: forall key0 V0 n out_len, 0 <= (n * 32)%Z <= out_len -> (n * 32)%Z <> out_len -> fst (HMAC_DRBG_generate_helper_Z HMAC256 key0 V0 ((n * 32)%Z + Z.min 32 (out_len - (n * 32)%Z))) = HMAC256 (fst (HMAC_DRBG_generate_helper_Z HMAC256 key0 V0 (n * 32)%Z)) key0.