#include<bits/stdc++.h>
#define int long long
using namespace std;
int a[1000010],tree[4000010],lazy1[4000010],lazy2[4000010];
bool lazy2u[4000010];//lazy1为add，lazy2为cover 
int op,n,q,L,R,x;
void update(int num){
	tree[num]=max(tree[num<<1],tree[num<<1|1]);
}
void build(int l,int r,int num){
	lazy2[num]=0;
	tree[num]=-1e9-1;
	if(l==r){
		tree[num]=a[l];
		return;
	}
	int mid=(l+r)>>1;
	build(l,mid,num<<1);
	build(mid+1,r,num<<1|1);
	update(num);
	return;
}
void push_down(int num){
	if(lazy2u[num]){
		lazy1[num<<1]=lazy1[num];
		lazy1[num<<1|1]=lazy1[num];
		lazy2[num<<1]=lazy2[num];
		lazy2[num<<1|1]=lazy2[num];
		tree[num<<1]=lazy1[num]+lazy2[num];
		tree[num<<1|1]=lazy1[num]+lazy2[num];
		lazy2u[num<<1]=lazy2u[num<<1|1]=1;
	}else{
		lazy1[num<<1]=lazy1[num];
		lazy1[num<<1|1]=lazy1[num];
		tree[num<<1]+=lazy1[num];
		tree[num<<1|1]+=lazy1[num];
	}
	lazy2u[num]=lazy1[num]=lazy2[num]=0;
}
void modify(int wl,int wr,int l,int r,int num,int x){
	if(wl<=l&&wr>=r){
		lazy1[num]+=x;
		tree[num]+=x;
		return;
	}
	push_down(num);
	int mid=(l+r)>>1;
	if(mid>=wl)modify(wl,wr,l,mid,num<<1,x);
	if(mid<wr)modify(wl,wr,mid+1,r,num<<1|1,x);
	update(num);
	return;
}
void cover(int wl,int wr,int l,int r,int num,int x){
	if(wl<=l&&wr>=r){
		lazy1[num]=0;
		lazy2[num]=x;
		tree[num]=x;
		lazy2u[num]=1;
		return;
	}
	push_down(num);
	int mid=(l+r)>>1;
	if(mid>=wl)cover(wl,wr,l,mid,num<<1,x);
	if(mid<wr)cover(wl,wr,mid+1,r,num<<1|1,x);
	update(num);
	return;
}
int findm(int wl,int wr,int l,int r,int num){
	if(wl<=l&&wr>=r){
		return tree[num];
	}
	push_down(num);
	int mid=(l+r)>>1,ans=-1e9-1;
	if(mid>=wl)ans=max(ans,findm(wl,wr,l,mid,num<<1));
	if(mid<wr)ans=max(ans,findm(wl,wr,mid+1,r,num<<1|1));
	update(num);
	return ans;
}
signed main(){
	scanf("%d%d",&n,&q);
	for(int i=1;i<=n;i++){
		scanf("%lld",a+i);
	}
	build(1,n,1);
	for(int i=1;i<=q;i++){
		scanf("%d",&op);
		if(op==1){
			scanf("%d%d%lld",&L,&R,&x);
			cover(L,R,1,n,1,x);
		}else if(op==2){
			scanf("%d%d%lld",&L,&R,&x);
			modify(L,R,1,n,1,x);
		}else{
			scanf("%d%d",&L,&R);
			printf("%lld\n",findm(L,R,1,n,1));
		}
	}
	return 0;
}