（#10数据文件过大无法下载。。）

#include <iostream>
#include <algorithm>
using namespace std;
typedef long long ll;

const int MAXN = 1e5 + 3;
const ll inf = 1e18 + 3;

int n, m;
ll a[MAXN];

struct node {
	int l, r;
	ll w;
	ll add, set;
} tree[MAXN * 4];

void pushup(int u) {
	tree[u].w = max(tree[u * 2].w, tree[u * 2 + 1].w);
}

void build(int u, int l, int r) {
	tree[u].l = l;
	tree[u].r = r;
	tree[u].set = inf;
	if (l == r) {
		tree[u].w = a[l];
		return;
	}
	int mid = l + r >> 1;
	build(u * 2, l, mid); build(u * 2 + 1, mid + 1, r);
	pushup(u);
}

inline bool inRange(int l, int r, int L, int R) {
	return l >= L && r <= R;
}

inline bool outOfRange(int l, int r, int L, int R) {
	return r < L || l > R;
}

void makeAddTag(int u, ll x) {
	if (tree[u].set == inf)
		tree[u].add += x;
	else
		tree[u].set += x;
	tree[u].w += x;
}

void makeSetTag(int u, ll x) {
	tree[u].add = 0;
	tree[u].set = x;
	tree[u].w = x;
}

void pushdown(int u) {
	if (tree[u].set == inf) {
		makeAddTag(u * 2, tree[u].add);
		makeAddTag(u * 2 + 1, tree[u].add);
		tree[u].add = 0;
	}
	else {
		makeSetTag(u * 2, tree[u].set);
		makeSetTag(u * 2 + 1, tree[u].set);
		tree[u].set = inf;
	}
}

ll query(int u, int L, int R) {
	if (inRange(tree[u].l, tree[u].r, L, R))
		return tree[u].w;
	if (!outOfRange(tree[u].l, tree[u].r, L, R)) {
		pushdown(u);
		return max(query(u * 2, L, R), query(u * 2 + 1, L, R));
	}
	return -inf;
}

void add(int u, int L, int R, ll x) {
	if (inRange(tree[u].l, tree[u].r, L, R))
		makeAddTag(u, x);
	else if (!outOfRange(tree[u].l, tree[u].r, L, R)) {
		pushdown(u);
		add(u * 2, L, R, x);
		add(u * 2 + 1, L, R, x);
		pushup(u);
	}
}

void set(int u, int L, int R, ll x) {
	if (inRange(tree[u].l, tree[u].r, L, R))
		makeSetTag(u, x);
	else if (!outOfRange(tree[u].l, tree[u].r, L, R)) {
		pushdown(u);
		set(u * 2, L, R, x);
		set(u * 2 + 1, L, R, x);
		pushup(u);
	}
}

int main() {
	cin.tie(nullptr) -> sync_with_stdio(false);
	cin >> n >> m;
	for (int i=1; i<=n; i++)
		cin >> a[i];
	build(1, 1, MAXN);
	for (int i=0; i<m; i++) {
		int op, x, y;
		cin >> op;
		switch (op) {
			case 1:
				ll k1;
				cin >> x >> y >> k1;
				set(1, x, y, k1);
				break;
			case 2:
				ll k2;
				cin >> x >> y >> k2;
				add(1, x, y, k2);
				break;
			case 3:
				cin >> x >> y;
				cout << query(1, x, y) << "\n";
		}
	}
	return 0;
}