#include <bits/stdc++.h>

using namespace std;

struct tree
{
	int l, r, value, lazy, s1, s2, flag;
	
	tree()
	{
		lazy = -1;
		value = 0;
		s1 = s2 = 0;
	}
};

int n, q, arr[1000005];
tree t[1000005];

void lazy1(int pos, int x)
{
	t[pos].lazy = x;
	t[pos].value = x;
	t[pos].flag = 1;
	
	return;
}

void lazy2(int pos, int x)
{
	t[pos].lazy = x;
	t[pos].value += x;
	t[pos].flag = 2;
	
	return;
}

void pushdown(int pos)
{
	if (t[pos].flag == 1)
	{
		lazy1(t[pos].s1, t[pos].lazy);
		lazy1(t[pos].s2, t[pos].lazy);
	}
	else
	{
		lazy2(t[pos].s1, t[pos].lazy);
		lazy2(t[pos].s2, t[pos].lazy);
	}
	
	t[pos].lazy = -1;
	
	return;
}

int build(int pos, int l, int r)
{
	t[pos].l = l;
	t[pos].r = r;
	
	if (l == r)
	{
		t[pos].value = arr[l];
		
		return t[pos].value;
	}
	
	t[pos].s1 = pos * 2;
	t[pos].s2 = pos * 2 + 1;
	t[pos].value = max(build(t[pos].s1, l, (l + r) / 2), build(t[pos].s2, (l + r) / 2 + 1, r));
	
	return t[pos].value;
}

int update(int pos, int l, int r, int x, int f)
{
	if (t[pos].lazy != -1)
		pushdown(pos);
	
	if (l <= t[pos].l && r >= t[pos].r)
	{
		if (f == 1)
			lazy1(pos, x);
		else
			lazy2(pos, x);
		
		return t[pos].value;
	}
	
	int mid = (t[pos].l + t[pos].r) / 2;
	
	if (l <= mid || r <= mid)
		update(t[pos].s1, l, r, x, f);
	
	if (l > mid || r > mid)
		update(t[pos].s2, l, r, x, f);
	
	t[pos].value = max(t[t[pos].s1].value, t[t[pos].s2].value);
	
	return t[pos].value;
}

int query(int pos, int l, int r)
{
	if (t[pos].lazy != -1)
		pushdown(pos);
	
	if (l <= t[pos].l && r >= t[pos].r)
		return t[pos].value;
	
	int mid = (t[pos].l + t[pos].r) / 2, maxx = -0x7ffffff;
	
	if (l <= mid || r <= mid)
		maxx = max(maxx, query(t[pos].s1, l, r));
	
	if (l >= mid || r > mid)
		maxx = max(maxx, query(t[pos].s2, l, r));
	
	t[pos].value = max(t[t[pos].s1].value, t[t[pos].s2].value);
	
	return maxx;
}

int main()
{
	int i;
	
	cin >> n >> q;
	
	for (i = 1; i <= n; i++)
		cin >> arr[i];
	
	build(1, 1, n);
	
	for (i = 1; i <= q; i++)
	{
		int op, l, r, x;
		
		cin >> op;
		
		if (op != 3)
		{
			cin >> l >> r >> x;
			
			update(1, l, r, x, op);
		}
		else
		{
			cin >> l >> r;
			
			cout << query(1, l, r) << endl;
		}
	}
	
	return 0;
}