#include <iostream>
#define int long long

#define ls(p) (p << 1)
#define rs(p) (p << 1 | 1)

using namespace std;

const int N = 1e6 + 5;

int t1[N << 2], t2[N << 2];
int t[N << 2], inf = 1145148100;
int n, m;

void cover(int p, int l, int r, int k)
{
	if (k == -inf) return;
	t1[p] = 0;
	t2[p] = t[p] = k;
}

void add(int p, int l, int r, int k)
{
	if (k == 0) return;

	int mid = (l + r) >> 1;
	cover(ls(p), l, mid + 1, t2[p]);
	cover(rs(p), mid + 1, r, t2[p]);
	t1[p] += k;
	t[p] += k;
}

void push_down(int p, int l, int r)
{
	int mid = (l + r) >> 1;
	cover(ls(p), l, mid, t2[p]);
	cover(rs(p), mid + 1, r, t2[p]);
	add(ls(p), l, mid, t1[p]);
	add(rs(p), mid + 1, r, t1[p]);
	t2[p] = -inf, t1[p] = 0;
}

void build(int p, int l, int r)
{
	if (l == r)
	{
		scanf("%lld", &t[p]);
		return;
	}
	int mid = (l + r) >> 1;
	build(ls(p), l, mid);
	build(rs(p), mid + 1, r);
	t[p] = max(t[ls(p)], t[rs(p)]); // push_up
}

void update(int x, int y, int op, int k, int p, int l, int r)
{
	if (x <= l && r <= y)
	{
		if (op == 1) cover(p, l, r, k); // op == 1 是覆盖！
		if (op == 2) add(p, l, r, k); // op == 2 是加法！
		return;
	}
	push_down(p, l, r);
	int mid = (l + r) >> 1;
	if (x <= mid) update(x, y, op, k, ls(p), l, mid);
	if (y >  mid) update(x, y, op, k, rs(p), mid + 1, r);
	t[p] = max(t[ls(p)], t[rs(p)]); // push_up
}

int query(int x, int y, int p, int l, int r)
{
	if (x <= l && r <= y) return t[p];
	push_down(p, l, r);
	int res = -inf;
	int mid = (l + r) >> 1;
	if (x <= mid) res = max(res, query(x, y, ls(p), l, mid));
	if (y >  mid) res = max(res, query(x, y, rs(p), mid + 1, r));
	return res;
}

signed main()
{
	scanf("%lld%lld", &n, &m);
	build(1, 1, n);
	for (int i = 1; i <= n * 4; i ++ ) t2[i] = -inf;
	int op, x, y, k;
	while (m -- )
	{
		scanf("%lld%lld%lld", &op, &x, &y);
		if (op <= 2) scanf("%lld", &k), update(x, y, op, k, 1, 1, n);
		else printf("%lld\n", query(x, y, 1, 1, n));
	}
	return 0;
}