#include<bits/stdc++.h>
using namespace std;
#define LL long long
#define ls p << 1
#define rs p << 1 | 1
const int N = 1e6 + 10;
int n, q, a[N], op, x, y, z;
struct T
{
	int l, r, t, add, maxv;
	bool f;
}t[N << 3];
void build(int p, int l, int r)
{
	t[p].l = l, t[p].r = r, t[p].add = t[p].f = 0;
	if(l == r)
	{
		t[p].maxv = a[l];
		return;
	}
	int mid = l + r >> 1;
	build(ls, l, mid), build(rs, mid + 1, r);
	t[p].maxv = max(t[ls].maxv, t[rs].maxv);
}
void pushdown1(int p)
{
	if(t[p].f)
	{
		t[ls].add = t[rs].add = 0;
		t[ls].maxv = t[rs].maxv = t[p].t;
		t[ls].t = t[rs].t = t[p].t;
		t[p].f = 0, t[ls].f = t[rs].f = 1;
	}
}
void pushdown2(int p)
{
	if(t[p].add)
	{	
		pushdown1(p);
		t[ls].maxv += t[p].add, t[rs].maxv += t[p].add; 
		t[ls].add += t[p].add, t[rs].add += t[p].add;
		t[p].add = 0;
	}
}
void change1(int p, int l, int r, int k)
{
	pushdown1(p); 
	if(l <= t[p].l && t[p].r <= r)
	{
		t[p].maxv += k;
		t[p].add += k;
		return;
	}
	pushdown2(p);
	int mid = t[p].l + t[p].r >> 1;
	if(l <= mid) change1(ls, l, r, k);
	if(r > mid) change1(rs, l, r, k);
	t[p].maxv = max(t[ls].maxv, t[rs].maxv);
}
void change2(int p, int l, int r, int k)
{
	if(l <= t[p].l && t[p].r <= r)
	{
		t[p].add = 0;
		t[p].maxv = k;
		t[p].t = k;
		t[p].f = 1;
		return;
	}
	pushdown1(p), pushdown2(p);
	int mid = t[p].l + t[p].r >> 1;
	if(l <= mid) change2(ls, l, r, k);
	if(r > mid) change2(rs, l, r, k);
	t[p].maxv = max(t[ls].maxv, t[rs].maxv);
}
LL ask(int p, int x, int y)
{
	LL ans = -1e15;
	if(x <= t[p].l && t[p].r <= y) return t[p].maxv;
	pushdown1(p), pushdown2(p);
	int mid = t[p].l + t[p].r >> 1;
	if(x <= mid) ans = max(ans, ask(ls, x, y));
	if(y > mid) ans = max(ans, ask(rs, x, y));
	return ans;
}
int main()
{

	cin >> n >> q;
	for(int i = 1; i <= n; i ++)
		scanf("%d", &a[i]);
	build(1, 1, n);
	while(q --)
	{
		scanf("%d%d%d", &op, &x, &y);
		if(op == 1)
		{
			scanf("%d", &z);
			change2(1, x, y, z);
		}
		if(op == 2)
		{
			scanf("%d", &z);
			change1(1, x, y, z);
		}
		if(op == 3) cout << ask(1, x, y) << "\n";
	}
	return 0;
}