#include <iostream>
#include <algorithm>
using namespace std;
const int N = 1e6 + 10;
typedef long long LL;
int n, m;


struct Node
{
	int l, r;
	LL add, change ,maxv;
}tr[N * 4];
LL a[N];
bool st = false;

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

void pushdown(int u)
{
	Node& root = tr[u], &left = tr[u << 1], &right = tr[u << 1 | 1];

	if (root.add != 0)
	{
		left.add += root.add, left.maxv += root.add;
		right.add += root.add, right.maxv += root.add;
		root.add = 0;
	}
	if (st == true)
	{
		left.change = root.change, left.maxv = root.change;
		right.change = root.change, right.maxv = root.change;
		st = false;
	}
}

void modify(int u, int l, int r, int x)
{
	if (tr[u].l >= l && tr[u].r <= r)
	{
		tr[u].maxv += x;
		tr[u].add += x;
	}
	else
	{
		st = false;
		pushdown(u);
		int mid = tr[u].l + tr[u].r >> 1;
		if (l <= mid) modify(u << 1, l, r, x);
		if (r > mid) modify(u << 1 | 1, l, r, x);
		pushup(u);
	}
}

void cmodify(int u, int l, int r, int x)
{
	if (tr[u].l >= l && tr[u].r <= r)
	{
		tr[u].maxv = x;
		tr[u].change = x;
		tr[u].add = 0;
	}
	else
	{
		st = true;
		tr[u].add = 0;
		pushdown(u);
		int mid = tr[u].l + tr[u].r >> 1;
		if (l <= mid) cmodify(u << 1, l, r, x);
		if (r > mid) cmodify(u << 1 | 1, l, r, x);
		pushup(u);
	}
}

LL query(int u, int l, int r)
{
	if (tr[u].l >= l && tr[u].r <= r)
		return tr[u].maxv;
	
	pushdown(u);
	LL maxn = -1e17;
	int mid = tr[u].l + tr[u].r >> 1;
	if (l <= mid) maxn = max(maxn , query(u << 1, l, r));
	if (r > mid) maxn = max(maxn, query(u << 1 | 1, l, r));
	return maxn;
}

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



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