#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define MINLL -1e12;

const int MAXN = 1e6 + 7;

ll tree[4 * MAXN], mark_plus[4 * MAXN], num[MAXN], mark_exch[4 * MAXN];
ll n, m;
bool exchanged[4 * MAXN];

inline void read(ll& a) {
	ll s = 0, w = 1;
	char ch = getchar();
	while (ch < '0' || ch > '9') {
		if (ch == '-')
			w = -1;
		ch = getchar();
	}
	while (ch >= '0' && ch <= '9') {
		s = s * 10 + ch - '0';
		ch = getchar();
	}
	a = s * w;
}

void build(ll l, ll r, ll p) {
	if (l == r) {
		tree[p] = num[l];
		return;
	}
	ll mid = (l + r) / 2;
	build(l, mid, p * 2);
	build(mid + 1, r, p * 2 + 1);
	tree[p] = max(tree[p * 2], tree[p * 2 + 1]);
}

void pushdown(ll p) {
	if (exchanged[p]) {
		mark_exch[p * 2] = mark_exch[p];
		mark_exch[p * 2 + 1] = mark_exch[p];
		tree[p * 2] = mark_exch[p];
		tree[p * 2 + 1] = mark_exch[p];
		exchanged[p * 2] = 1;
		exchanged[p * 2 + 1] = 1;
		exchanged[p] = 0;
	}
	mark_plus[p * 2] += mark_plus[p];
	mark_plus[p * 2 + 1] += mark_plus[p];
	tree[p * 2] += mark_plus[p];
	tree[p * 2 + 1] += mark_plus[p];;
	mark_plus[p] = 0;
	return;
}

void update(ll l, ll r, ll cl, ll cr, ll p, ll v) {
	if (r < cl || l > cr)return;
	if (cl >= l && cr <= r) {
		tree[p] += v;
		if (cr != cl)mark_plus[p] += v;
		return;
	}
	ll mid = (cl + cr) / 2;
	pushdown(p);
	update(l, r, cl, mid, p * 2, v);
	update(l, r, mid + 1, cr, p * 2 + 1, v);
	tree[p] = max(tree[p * 2], tree[p * 2 + 1]);
	return;

}

void clear(ll l, ll r, ll cl, ll cr, ll p, ll v) {

	if (r < cl || l > cr)return;
	if (cl >= l && cr <= r) {
		tree[p] = v;
		mark_plus[p] = 0;
		mark_exch[p] = v;
		exchanged[p] = 1;
		return;
	}
	ll mid = (cl + cr) / 2;
	pushdown(p);
	clear(l, r, cl, mid, p * 2, v);
	clear(l, r, mid + 1, cr, p * 2 + 1, v);
	tree[p] = max(tree[p * 2], tree[p * 2 + 1]);
	return;
}

ll get(ll l, ll r, ll cl, ll cr, ll p) {
	if (r < cl || l > cr)return MINLL;
	if (cl >= l && cr <= r) {
		return tree[p];
	}
	ll mid = (cl + cr) / 2;
	pushdown(p);;
	return max(get(l, r, cl, mid, p * 2), get(l, r, mid + 1, cr, p * 2 + 1));
}
int main() {
	freopen("P1253_7.in","r",stdin);
	freopen("P1253_7ma.out","w",stdout);
	cin >> n >> m;
	for (ll i = 1; i <= n; i++)read(num[i]);
	build(1, n, 1);
	for (ll i = 1; i <= m; i++) {
		ll op, l, r, x;
		read(op);
		read(l);
		read(r);
		switch (op) {
			case 1:
				read(x);
				clear(l, r, 1, n, 1, x);
				break;
			case 2:
				read(x);
				update(l, r, 1, n, 1, x);
				break;
			case 3:
				printf("%lld\n", get(l, r, 1, n, 1));
				break;
		}
	}
}
/*
6 6
1 1 4 5 1 4
1 1 2 6
2 3 4 2
3 1 4
3 2 3
1 1 6 -1
3 1 6



*/

后四个点WA，估计是标记在哪里打错了，查了一晚上都没查出来，更玄学的是如果每一步都get一次下一次的有一些点就对了，求大佬帮忙看看，非常感谢