need = subTreeIndex(lo, lo+k, need)
		need = leafProofIndex(lo+k, hi, n, need)
	}
	return need
}

// leafProof constructs the proof that leaf n is contained in the subtree with leaves [lo, hi).
// It returns any leftover hashes as well.
// See https://tools.ietf.org/html/rfc6962#section-2.1.1
func leafProof(lo, hi, n int64, hashes []Hash) (RecordProof, []Hash) {
	// We must have lo <= n < hi or else the code here has a bug.