#include<iostream>
#define lc p << 1
#define rc p << 1 | 1 
#define int long long
using namespace std;
const int maxn = 1e6 + 1;
const int inf = 1e18;
struct Tree{
	int l,r,sum,add,cover;
}tr[maxn << 2];
int n,p,a[maxn];
void build(int p,int l,int r){
	tr[p] = (Tree) {l,r,a[l],0,inf};
	if(l == r) return;
	int m = l + (r - l >> 1);
	build(lc,l,m);
	build(rc,m+1,r);
	tr[p].sum = max(tr[lc].sum,tr[rc].sum);
}
void cupdate(int p,int l,int r,int x){
	if(l <= tr[p].l && tr[p].r <= r){
		tr[p].sum = x;
		tr[p].cover = x;
		tr[p].add = 0;
		return;
	}
	if(tr[p].cover != inf){
		tr[lc].sum = tr[rc].sum = tr[p].cover;
		tr[lc].cover = tr[rc].cover = tr[p].cover;
		tr[lc].add = tr[rc].add = 0;
		tr[p].cover = inf;
	}
	if(tr[p].add){
		tr[lc].sum += tr[p].add;
		tr[rc].sum += tr[p].add;
		tr[lc].add += tr[p].add;
		tr[rc].add += tr[p].add;
		tr[p].add = 0;
	}
	int m = tr[p].l + (tr[p].r - tr[p].l >> 1);
	if(l <= m) cupdate(lc,l,r,x);
	if(r > m) cupdate(rc,l,r,x);
	tr[p].sum = max(tr[lc].sum,tr[rc].sum);
}
void aupdate(int p,int l,int r,int x){
	if(l <= tr[p].l && tr[p].r <= r){
		tr[p].sum += x;
		tr[p].add += x;
		return;
	}
	if(tr[p].cover != inf){
		tr[lc].sum = tr[rc].sum = tr[p].cover;
		tr[lc].cover = tr[rc].cover = tr[p].cover;
		tr[lc].add = tr[rc].add = 0;
		tr[p].cover = inf;
	}
	if(tr[p].add){
		tr[lc].sum += tr[p].add;
		tr[rc].sum += tr[p].add;
		tr[lc].add += tr[p].add;
		tr[rc].add += tr[p].add;
		tr[p].add = 0;
	}
	int m = tr[p].l + (tr[p].r - tr[p].l >> 1);
	if(l <= m) aupdate(lc,l,r,x);
	if(r > m) aupdate(rc,l,r,x);
	tr[p].sum = max(tr[lc].sum,tr[rc].sum);
}
int query(int p,int x,int y){
	if(x <= tr[p].l && tr[p].r <= y) return tr[p].sum;
	if(tr[p].cover != inf){
		tr[lc].sum = tr[rc].sum = tr[p].cover;
		tr[lc].cover = tr[rc].cover = tr[p].cover;
		tr[lc].add = tr[rc].add = 0;
		tr[p].cover = inf;
	}
	if(tr[p].add){
		tr[lc].sum += tr[p].add;
		tr[rc].sum += tr[p].add;
		tr[lc].add += tr[p].add;
		tr[rc].add += tr[p].add;
		tr[p].add = 0;
	}
	int m = tr[p].l + (tr[p].r - tr[p].l >> 1),maxx = -inf;
	if(x <= m) maxx = query(lc,x,m);
	if(y > m) maxx = max(maxx,query(rc,m+1,y));
	return maxx;
}
signed main(){
	scanf("%lld%lld",&n,&p);
	for(int i = 1;i <= n;++i) scanf("%lld",&a[i]);
	build(1,1,n);
	for(int i = 0,opt,l,r,x;i < p;++i){
		scanf("%lld%lld%lld",&opt,&l,&r);
		if(opt == 1){
			scanf("%lld",&x);
			cupdate(1,l,r,x);
		}else if(opt == 2){
			scanf("%lld",&x);
			aupdate(1,l,r,x);
		}else printf("%lld\n",query(1,l,r));
	}
	return 0;
}