// Problem: P1253 扶苏的问题
// Contest: Luogu
// URL: https://www.luogu.com.cn/problem/P1253
// Memory Limit: 512 MB
// Time Limit: 2000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
typedef long long ll;
const int N=1000010;
const ll INF=1e20;

int n,q;
int w[N];
struct Node{
	int l,r;
	ll Max,f1,f2;
}tr[N*4];

void pushup(int u)
{
	tr[u].Max=max(tr[u<<1].Max,tr[u<<1|1].Max);
}

void pushdown(int u)
{
	if(tr[u].f1!=INF)
	{
		tr[u].f2=tr[u<<1].f2=tr[u<<1|1].f2=0;
		tr[u<<1].f1=tr[u].f1;
		tr[u<<1].Max=tr[u].f1;
		tr[u<<1|1].f1=tr[u].f1;
		tr[u<<1|1].Max=tr[u].f1;
		tr[u].f1=INF;
	}
	else
	{
		tr[u<<1].f2+=tr[u].f2;
		tr[u<<1].Max+=tr[u].f2;
		tr[u<<1|1].f2+=tr[u].f2;
		tr[u<<1|1].Max+=tr[u].f2;
		tr[u].f2=0;
	}
}

void build(int u,int l,int r)
{
	if(l==r) tr[u]={l,r,w[r],INF,0};
	else 
	{
		tr[u]={l,r,0,INF,0};
		int mid=l+r>>1;
		build(u<<1,l,mid);
		build(u<<1|1,mid+1,r);
		pushup(u);
	}
}

void modify(int u,int l,int r,ll f,ll a)
{
	Node &ro=tr[u];
	if(ro.l>=l&&ro.r<=r)
	{
		if(f!=INF)
		{
			ro.Max=f;
			tr[u].f1=f;
		}
		else
		{
			ro.Max+=a;
			ro.f2+=a;
		}
	}
	else 
	{
		pushdown(u);
		int mid=ro.l+ro.r>>1;
		if(l<=mid) modify(u<<1,l,r,f,a);
		if(r>mid) modify(u<<1|1,l,r,f,a);
		pushup(u);
	}
}

ll query(int u,int l,int r)
{
	Node &ro=tr[u]; 
	if(ro.l>=l&&ro.r<=r) return tr[u].Max;
	ll res = -INF;
	pushdown(u);
	int mid=ro.l+ro.r>>1;
	if(l<=mid) res = max(res, query(u<<1,l,r));
	if(r>mid) res = max(res, query(u<<1|1,l,r));
	return res;
}

int main()
{
	scanf("%d%d",&n,&q);
	for(int i=1;i<=n;i++) scanf("%d",&w[i]);
	build(1,1,n);
	for(int i = 1; i <= n; i ++)  query(1, i, i);
	int op,l,r,x;
	while(q--)
	{
		scanf("%d%d%d",&op,&l,&r);
		if(op==1)
		{
			scanf("%d",&x);
			modify(1,l,r,x,0);
		}
		else if(op==2)
		{
			scanf("%d",&x);
			modify(1,l,r,INF,x);
		}
		else printf("%lld\n",query(1,l,r));
	}
	return 0;
}