#include<iostream>
#include<string>
#include<cstdio>
using namespace std;
const int N = 2000001;
typedef long long LL;
struct node {
	LL l, r, maxn, cover, add;
	bool st;
} tr[N * 8];
int n, q, w[N];
void pushup(int u) {
	tr[u].maxn = max(tr[u << 1].maxn, tr[u << 1 | 1].maxn);
}
void pushdown1(int u) {
	node &a = tr[u], &l = tr[u << 1], &r = tr[u << 1 | 1];
	if (a.add) {
		l.add += a.add, l.maxn += l.add;
		r.add += a.add, r.maxn += r.add;
		a.add = 0;
	}
}
void pushdown2(int u) {
	node &a = tr[u], &l = tr[u << 1], &r = tr[u << 1 | 1];
	if (a.st == 1) {
		l.cover = a.cover, l.maxn = a.cover;
		r.cover = a.cover, r.maxn = a.cover;
		l.add = r.add = a.add = 0;
		a.st = 0;
	}
}
void build(int u, int l, int r) {
	if (l == r) {
		tr[u] = {l, r, w[l], w[l], 0, 0};
		return;
	} else {
		tr[u] = {l, r};
		int mid = tr[u].l + tr[u].r >> 1;
		build(u << 1, l, mid), build(u << 1 | 1, mid + 1, r);
		pushup(u);
	}
}
void modify_add(int u, int l, int r, int add) {
	if (tr[u].l >= l && tr[u].r <= r) {
		tr[u].maxn += add;
		tr[u].add += add;
	} else {
		pushdown1(u);
		int mid = tr[u].l + tr[u].r >> 1;
		if (l <= mid) modify_add(u << 1, l, r, add);
		if (r > mid) modify_add(u << 1 | 1, l, r, add);
		pushup(u);
	}
}
void modify_cover(int u, int l, int r, int c) {
	if (tr[u].l >= l && tr[u].r <= r) {
		tr[u].cover = c;
		tr[u].maxn = c;
		tr[u].add = 0;
		tr[u].st = 1;
	} else {
		pushdown2(u);
		int mid = tr[u].l + tr[u].r >> 1;
		if (l <= mid) modify_cover(u << 1, l, r, c);
		if (r > mid) modify_cover(u << 1 | 1, l, r, c);
		pushup(u);
	}
}
LL query(int u, int l, int r) {
	if (tr[u].l >= l && tr[u].r <= r) {
		return tr[u].maxn;
	}
	pushdown2(u);
	pushdown1(u);
	int mid = tr[u].l + tr[u].r >> 1;
	LL maxx = -0x3f3f3f3f;
	if (l <= mid) maxx = max(query(u << 1, l, r), maxx);
	if (r > mid) maxx = max(query(u << 1 | 1, l, r), maxx);
	return maxx;
}
int main() {
	scanf("%d%d", &n, &q);
	for (int i = 1; i <= n; i++) {
		scanf("%d", &w[i]);
	}
	build(1, 1, n);
	while (q--) {
		int op;
		scanf("%d", &op);
		if (op == 1) {
			int l, r, x;
			scanf("%d%d%d", &l, &r, &x);
			modify_cover(1, l, r, x);
		} else if (op == 2) {
			int l, r, x;
			scanf("%d%d%d", &l, &r, &x);
			modify_add(1, l, r, x);
		} else {
			int l, r;
			scanf("%d%d", &l, &r);
			printf("%lld\n", query(1, l, r));
		}
	}
	return 0;
}