#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N = 1000010, inf = 2e9;
struct node {
	int u, l, r, mx, lzy1, lzy2;
} tr[N * 4];
int a[N];
void pushup(int u) {
	tr[u].mx = max(tr[u << 1].mx, tr[u << 1 | 1].mx);
}
void cvdown(int u) {
	if(tr[u].lzy2 != inf) {
		tr[u].lzy1 = 0;
		tr[u << 1].lzy1 = tr[u << 1 | 1].lzy1 = 0;
		tr[u << 1].mx = tr[u << 1 | 1].mx = tr[u].lzy2;
		tr[u << 1].lzy2 = tr[u << 1 | 1].lzy2 = tr[u].lzy2;
		tr[u].lzy2 = inf;
	}
}
void addown(int u) {
	if(tr[u].lzy1) {
		tr[u << 1].mx += tr[u].lzy1, tr[u << 1 | 1].mx += tr[u].lzy1;
		tr[u << 1].lzy1 += tr[u].lzy1, tr[u << 1 | 1].lzy1 += tr[u].lzy1;
		tr[u].lzy1 = 0;
	}
}
void pushdown(int u) {
	cvdown(u); addown(u);
}
void build(int u, int l, int r) {
	tr[u].l = l, tr[u].r = r; tr[u].lzy2 = inf;
	if(l == r) {
		tr[u].mx = a[l];
		return ;
	}
	int mid = l + r >> 1;
	build(u << 1, l, mid);
	build(u << 1 | 1, mid + 1, r);
	pushup(u);
}
void Add(int u, int l, int r, int L, int R, int v) {
	if(L <= l && R >= r) {
		cvdown(u);
		tr[u].mx += v;
		tr[u].lzy1 += v;
		return ;
	}
	pushdown(u);
	int mid = l + r >> 1;
	if(L <= mid) Add(u << 1, l, mid, L, R, v);
	if(mid < R) Add(u << 1 | 1, mid + 1, r, L, R, v);
	pushup(u);
}
void cover(int u, int l, int r, int L, int R, int v) {
	if(L <= l && R >= r) {
		tr[u].lzy1 = 0;
		tr[u].mx = v;
		tr[u].lzy2 = v;
		return ;
	}
	pushdown(u);
	int mid = l + r >> 1;
	if(L <= mid) cover(u << 1, l, mid, L, R, v);
	if(mid < R) cover(u << 1 | 1, mid + 1, r, L, R, v);
	pushup(u);
}
int ask(int u, int l, int r, int L, int R) {
	if(L <= l && R >= r) {
		return tr[u].mx;
	}
	pushdown(u);
	int mid = l + r >> 1;
	int ans = -inf;
	if(L <= mid) ans = max(ans, ask(u << 1, l, mid, L, R));
	if(mid < R) ans = max(ans, ask(u << 1 | 1, mid + 1, r, L, R));
	return ans;
}
signed main() {
	ios::sync_with_stdio(0);
	int n, m;
	cin >> n >> m;
	for(int i = 1; i <= n; i++) cin >> a[i];
	build(1, 1, n);
	while(m--) {
		int o, l, r;
		cin >> o >> l >> r;
		if(o == 2) {
			int k; cin >> k;
			Add(1, 1, n, l, r, k);
		}
		else if(o == 1) {
			int k; cin >> k;
			cover(1, 1, n, l, r, k);
		}
		else {
			cout << ask(1, 1, n, l, r) << '\n';
		}
	}
	return 0;
}

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