Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
You can target 1 "Megalith" monster in your GY; Special Summon it in Defense Position, but place it on the bottom of the Deck when it leaves the field (even if this card leaves the field). You can only use this effect of "Megalith Emergence" once per turn.
--メガリス・エマージョン
--Megalith Emergence
--Scripted by Naim
local s,id=GetID()
function s.initial_effect(c)
	--Activate
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetCode(EVENT_FREE_CHAIN)
	e1:SetHintTiming(0,TIMING_END_PHASE)
	c:RegisterEffect(e1)
	--Special summon 1 "Megalith" monster from GY
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetCategory(CATEGORY_SPECIAL_SUMMON)
	e2:SetType(EFFECT_TYPE_QUICK_O)
	e2:SetCode(EVENT_FREE_CHAIN)
	e2:SetRange(LOCATION_SZONE)
	e2:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e2:SetCountLimit(1,id)
	e2:SetTarget(s.sptg)
	e2:SetOperation(s.spop)
	c:RegisterEffect(e2)
end
s.listed_series={SET_MEGALITH}
function s.spfilter(c,e,tp)
	return c:IsSetCard(SET_MEGALITH) and c:IsCanBeSpecialSummoned(e,0,tp,false,false,POS_FACEUP_DEFENSE)
end
function s.sptg(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsLocation(LOCATION_GRAVE) and chkc:IsControler(tp) and s.spfilter(chkc,e,tp) end
	if chk==0 then return Duel.GetLocationCount(tp,LOCATION_MZONE)>0 and Duel.IsExistingTarget(s.spfilter,tp,LOCATION_GRAVE,0,1,nil,e,tp) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_SPSUMMON)
	local g=Duel.SelectTarget(tp,s.spfilter,tp,LOCATION_GRAVE,0,1,1,nil,e,tp)
	Duel.SetOperationInfo(0,CATEGORY_SPECIAL_SUMMON,g,1,0,0)
end
function s.spop(e,tp,eg,ep,ev,re,r,rp)
	if not e:GetHandler():IsRelateToEffect(e) then return end
	local tc=Duel.GetFirstTarget()
	if tc:IsRelateToEffect(e) and Duel.SpecialSummonStep(tc,0,tp,tp,false,false,POS_FACEUP_DEFENSE) then
		--Return it to deck if it leaves the field
		local e1=Effect.CreateEffect(e:GetHandler())
		e1:SetDescription(3301)
		e1:SetType(EFFECT_TYPE_SINGLE)
		e1:SetCode(EFFECT_LEAVE_FIELD_REDIRECT)
		e1:SetProperty(EFFECT_FLAG_CANNOT_DISABLE+EFFECT_FLAG_CLIENT_HINT)
		e1:SetReset(RESET_EVENT|RESETS_REDIRECT)
		e1:SetValue(LOCATION_DECKBOT)
		tc:RegisterEffect(e1)
	end
	Duel.SpecialSummonComplete()
end