#include<bits/stdc++.h>
#define int long long
#define INT_MIN LLONG_MIN
using namespace std;
int n,m,tree[5000005],a[1000005],op,a1,a2,a3,lazytag1[5000005],lazytag2[2000005]; 
void pushup(int k)
{
	tree[k] = max(tree[k * 2],tree[k * 2 + 1]);
	lazytag2[k] = INT_MIN;
}
void add1(int k,int v)
{
	lazytag1[k] += v;
	tree[k] += lazytag1[k];
}
void add2(int k,int v)
{
	lazytag2[k] = v;
	tree[k] = lazytag2[k];
}
void pushdown2(int k)
{
	if(lazytag2[k] == INT_MIN)return;
	lazytag1[k] = 0;
	add2(k * 2,lazytag2[k]);
	add2(k * 2 + 1,lazytag2[k]);
	lazytag2[k] = INT_MIN;
}
void pushdown1(int k)
{
	pushdown2(k);
	if(lazytag1[k] == 0)return;
	add1(k * 2,lazytag1[k]);
	add1(k * 2 + 1,lazytag1[k]);
	lazytag1[k] = 0;
}
void build(int k,int l,int r)
{
	if(l == r)
	{
		tree[k] = a[l];
		return;
	}
	int mid = (l + r) >> 1;
	build(k * 2,l,mid);
	build(k * 2 + 1,mid + 1,r);
	pushup(k);
}
void update1(int k,int l,int r,int x,int y,int v)
{
	if(l > y || r < x)return;
	if(l >= x && r <= y)
	{
		//lazytag2[k] = 1e9 + 1;
		pushdown2(k);
		lazytag1[k] += v;
		tree[k] += v;
		return;
	}
	int  mid = (l + r) >> 1;
	pushdown1(k);
	update1(k * 2,l,mid,x,y,v);
	update1(k * 2 + 1,mid + 1,r,x,y,v);
	pushup(k);
}
void update2(int k,int l,int r,int x,int y,int v)
{
	if(l > y || r < x)return;
	if(l >= x && r <= y)
	{
		lazytag1[k] = 0;
		lazytag2[k] = v;
		tree[k] = v;
		return;
	}
	int  mid = (l + r) >> 1;
	pushdown2(k);
	update2(k * 2,l,mid,x,y,v);
	update2(k * 2 + 1,mid + 1,r,x,y,v);
	pushup(k);
}
int ask(int k,int l,int r,int x,int y)
{
	if(l > y || r < x)return INT_MIN;
	if(l >= x && r <= y)return tree[k];
	int mid = (l + r) >> 1;
	pushdown1(k);
	//pushdown2(k);
	return max(ask(k * 2,l,mid,x,y),ask(k * 2 + 1,mid + 1,r,x,y));
}
signed main()
{
	//freopen(".in","r",stdin);
	//freopen(".out","w",stdout);
	cin >> n >> m;
	for(int i = 1;i <= n;i ++)cin >> a[i];
	build(1,1,n);
	for(int i = 1;i <= m;i ++)
	{
		cin >> op;
		if(op == 1)
		{
			cin >> a1 >> a2 >> a3;
			update2(1,1,n,a1,a2,a3);
		}
		if(op == 2)
		{
			cin >> a1 >> a2 >> a3;
			update1(1,1,n,a1,a2,a3);
		}
		if(op == 3)
		{
			cin >> a1 >> a2;
			cout << ask(1,1,n,a1,a2) << endl;
		}
	}
	return 0;
}