#include<iostream>
using namespace std;
const int minn=-1e9-1;
const int N=1e6+6;
int n,q;
int a[N];
int op,l,r,x;
int f[N<<2];
int xg[N<<2],jia[N<<2];
bool visxg[N<<2];
int ans;
void build(int l,int r,int i){
	if(l==r){
		f[i]=a[l];
		return ;
	}
	int mid=(l+r)/2;
	build(l,mid,i*2);
	build(mid+1,r,i*2+1);
	f[i]=max(f[i*2],f[i*2+1]);
}
void tree1(int l,int r,int sl,int sr,int s,int i){
	if(l==r||(l==sl&&r==sr)){
		visxg[i]=1,xg[i]=s;
		jia[i]=0;
		f[i]=s;
		return ;
	}
	int mid=(l+r)/2;
	if(visxg[i]!=0) f[i*2]=xg[i],f[i*2+1]=xg[i],visxg[i]=0;
	f[i*2]+=jia[i],f[i*2+1]+=jia[i],jia[i]=0;
	if(sl<=mid) tree1(l,mid,sl,min(sr,mid),s,i*2);
	if(sr>mid) tree1(mid+1,r,max(sl,mid+1),sr,s,i*2+1);
	f[i]=max(f[i*2],f[i*2+1]);
}
void tree2(int l,int r,int sl,int sr,int s,int i){
	if(l==r||(l==sl&&r==sr)){
		jia[i]+=s;
		f[i]+=s;
		return ;
	}
	int mid=(l+r)/2;
	if(visxg[i]!=0) f[i*2]=xg[i],f[i*2+1]=xg[i],visxg[i]=0;
	f[i*2]+=jia[i],f[i*2+1]+=jia[i],jia[i]=0;
	if(sl<=mid) tree2(l,mid,sl,min(sr,mid),s,i*2);
	if(sr>mid) tree2(mid+1,r,max(sl,mid+1),sr,s,i*2+1);
	f[i]=max(f[i*2],f[i*2+1]);
}
void tree3(int l,int r,int sl,int sr,int i){
	if(l==r||(l==sl&&r==sr)){
		ans=max(ans,f[i]);
		return ;
	}
	int mid=(l+r)/2;
	if(visxg[i]!=0) f[i*2]=xg[i],f[i*2+1]=xg[i],visxg[i]=0;
	f[i*2]+=jia[i],f[i*2+1]+=jia[i],jia[i]=0;
	if(sl<=mid) tree3(l,mid,sl,min(sr,mid),i*2);
	if(sr>mid) tree3(mid+1,r,max(sl,mid+1),sr,i*2+1);
}
int main(){
	scanf("%d%d",&n,&q);
	for(int i=1;i<=n;i++) scanf("%d",&a[i]);
	build(1,n,1);
	while(q--){
		scanf("%d%d%d",&op,&l,&r);
		if(op==1){
			scanf("%d",&x);
			tree1(1,n,l,r,x,1);
		}
		else if(op==2){
			scanf("%d",&x);
			tree2(1,n,l,r,x,1);
		}
		else{
			ans=minn;
			tree3(1,n,l,r,1);
			printf("%d\n",ans);
		}
	}
	return 0;
}