#include<bits/stdc++.h>
#define int long long
using namespace std;

const int N = 1000005, INF = 1e17;
int n, q;
int a[N], tree[N * 4], add[N * 4], eqa[N * 4];

struct Segment_Tree{
	void pushdown(int k){
		if (eqa[k] != INF){
			tree[k << 1] = eqa[k << 1] = eqa[k];
			add[k << 1] = 0;
			tree[k << 1 | 1] = eqa[k << 1 | 1] = eqa[k];
			add[k << 1 | 1] = 0;
			eqa[k] = INF;
		}
		add[k << 1] += add[k];
		tree[k << 1] += add[k];
		add[k << 1 | 1] += add[k];
		tree[k << 1 | 1] += add[k];
		add[k] = 0;
	}
	void pushup(int k){
		tree[k] = max(tree[k << 1], tree[k << 1 | 1]);
	}
	void build(int k, int l, int r){
		eqa[k] = INF;
		if (l == r){
			tree[k] = a[l];
			return ;
		}
		int mid = (l + r) >> 1;
		build(k << 1, l, mid);
		build(k << 1 | 1, mid + 1, r);
		pushup(k);
	}
	void ud1(int k, int l, int r, int x, int y, int v){
		if (l >= x && r <= y){
			tree[k] = v;
			eqa[k] = v;
			return ;
		}
		pushdown(k);
		int mid = (l + r) >> 1;
		if (x <= mid) ud1(k << 1, l, mid, x, y, v);
		if (y >= mid + 1) ud1(k << 1 | 1, mid + 1, r, x, y, v);
		pushup(k);
	}
	void ud2(int k, int l, int r, int x, int y, int v){
		if (l >= x && r <= y){
			tree[k] += v;
			add[k] += v;
			return ;
		}
		pushdown(k);
		int mid = (l + r) >> 1;
		if (x <= mid) ud2(k << 1, l, mid, x, y, v);
		if (y >= mid + 1) ud2(k << 1 | 1, mid + 1, r, x, y, v);
		pushup(k);		
	}
	int ask(int k, int l, int r, int x, int y){
		if (l >= x && r <= y) return tree[k];
		pushdown(k);
		int mid = (l + r) >> 1, res = -INF;
		if (x <= mid) res = max(res, ask(k << 1, l, mid, x, y));
		if (y >= mid + 1) res = max(res, ask(k << 1 | 1, mid + 1, r, x, y));
		return res;
	}
}SGT;

signed main(){
//	freopen("P1253_7(1).in", "r", stdin);
//	freopen("P1253_7.ans", "w", stdout);
	scanf("%lld %lld", &n, &q);
	for (int i = 1; i <= n; i++){
		scanf("%lld", &a[i]);
	}
	SGT.build(1, 1, n);
	while(q--){
		int opt, l, r, x;
		scanf("%lld %lld %lld", &opt, &l, &r);
		if (opt == 1){
			scanf("%lld", &x);
			SGT.ud1(1, 1, n, l, r, x);
		}
		if (opt == 2){
			scanf("%lld", &x);
			SGT.ud2(1, 1, n, l, r, x);
		}
		if (opt == 3){
			printf("%lld\n", SGT.ask(1, 1, n, l, r));
		}
	}
	return 0;
}