#include<bits/stdc++.h>
#define ll long long
#define lson pos<<1 
#define rson pos<<1|1
using namespace std;
const int maxn=1e6+10;
const int mod=1e6+7;
int n;
ll m,t;
int a[maxn];
struct node{
	ll add,mx,re;
}tree[maxn*4];

void pushup(int pos){
	tree[pos].mx=max(tree[lson].mx,tree[rson].mx);
	return;
}

void pushdown(int pos,int l,int r){
	//cout<<l<<" "<<r<<" "<<tree[pos].re<<" "<<tree[pos].add<<" "<<tree[pos].mx<<endl;
	if(l==r) {tree[pos].add=0;tree[pos].re=1000000001;return;}
	if(tree[pos].re!=1000000001){
		tree[lson].mx=tree[rson].mx=tree[pos].re;
		tree[lson].re=tree[rson].re=tree[pos].re;
		tree[lson].add=tree[rson].add=0;
		tree[pos].re=1000000001;
		return;
	}
	if(tree[pos].add==0) return;
	tree[lson].mx+=tree[pos].add;
	tree[rson].mx+=tree[pos].add;
	tree[lson].add+=tree[pos].add;
	tree[rson].add+=tree[pos].add;
	return;
}

void build(int pos,int l,int r){
	if(l==r){
		tree[pos].re=1000000001;
		tree[pos].add=0;
		tree[pos].mx=a[l];
		return;
	}
	int mid=(l+r)/2;
	build(lson,l,mid);
	build(rson,mid+1,r);
	pushup(pos);
	return;
}

void change(int pos,int l,int r,int xl,int xr,int k){
	if(xl<=l&&r<=xr){
		tree[pos].re=tree[pos].mx=k;
		tree[pos].add=0;
		return;
	}
	pushdown(pos,l,r);
	int mid=(l+r)/2;
	if(xl<=mid) change(lson,l,mid,xl,xr,k);
	if(xr>mid) change(rson,mid+1,r,xl,xr,k);
	pushup(pos);
	return;
}

void plu(int pos,int l,int r,int xl,int xr,int k){
	pushdown(pos,l,r);
	if(xl<=l&&xr>=r){
		tree[pos].add+=k;
		tree[pos].mx+=k;
		return;
	}	
	int mid=(l+r)/2;
	if(xl<=mid) plu(lson,l,mid,xl,xr,k);
	if(xr>mid) plu(rson,mid+1,r,xl,xr,k);
	pushup(pos);
	return;
}

ll query(int pos,int l,int r,int xl,int xr){
	pushdown(pos,l,r);
	if(xl<=l&&r<=xr){
		return tree[pos].mx;
	}
	int mid=(l+r)/2;
	ll res=0;
	if(xl<=mid) res=max(res,query(lson,l,mid,xl,xr));
	if(xr>mid) res=max(res,query(rson,mid+1,r,xl,xr));
	return res;
}

int main(){
	scanf("%d%d",&n,&m);	
	for(int i=1;i<=n;i++){
		scanf("%d",&a[i]);
	}
	build(1,1,n);
	while(m--){
		int order,x,y,z;
		scanf("%d",&order);
		if(order==1){
			scanf("%d%d%d",&x,&y,&z);
			change(1,1,n,x,y,z);
		}
		else if(order==2){
			scanf("%d%d%d",&x,&y,&z);
			plu(1,1,n,x,y,z);
		}
		else{
			scanf("%d%d",&x,&y);
			ll res=query(1,1,n,x,y);
			printf("%lld\n",res);
		}
	}
	return 0;
}