#include<bits/stdc++.h>
#define int long long
using namespace std;
namespace Tree{
	const int maxn=1000005;
	int n,q;
	int val[maxn];
	struct tree{
		int l,r;
		int lson,rson;
		int maxx;
		int cov,add;
	}a[maxn*4];
	void pushup(int x){
		a[x].maxx=max(a[a[x].lson].maxx,a[a[x].rson].maxx);
	}
	int cnt=0;
	int Root;
	void Build(int &x,int l,int r){
		if(x==0){
			x=++cnt;
			a[x].l=l;
			a[x].r=r;
			a[x].add=0;
			a[x].cov=-1;
		}
		if(l==r){
			a[x].maxx=val[l];
			return ;
		}
		int mid=(l+r)/2;
		Build(a[x].lson,l,mid);
		Build(a[x].rson,mid+1,r);
		pushup(x);
	}
	void coverdown(int x){
		if(a[x].cov!=-1){
			a[a[x].lson].maxx=a[x].cov;
			a[a[x].rson].maxx=a[x].cov;
			a[a[x].lson].cov=a[x].cov;
			a[a[x].rson].cov=a[x].cov;
			a[x].cov=-1;
		}
	}
	void plusdown(int x){
		if(a[x].add!=0){
			a[a[x].lson].maxx+=a[x].add;
			a[a[x].rson].maxx+=a[x].add;
			a[a[x].lson].add+=a[x].add;
			a[a[x].rson].add+=a[x].add;
			a[x].add=0;
		}
	}
	void cover(int x,int l,int r,int y){
		if(a[x].r<l||a[x].l>r)
			return ;
		if(l<=a[x].l&&a[x].r<=r){
			a[x].maxx=y;
			a[x].cov=y;
			a[x].add=0;
			return ;
		}
		coverdown(x);
		int mid=(a[x].l+a[x].r)/2;
		if(l<=mid) cover(a[x].lson,l,r,y);
		if(mid<r) cover(a[x].rson,l,r,y);
		pushup(x);
	}
	void plus(int x,int l,int r,int y){
		if(a[x].r<l||a[x].l>r)
			return ;
		if(l<=a[x].l&&a[x].r<=r){
			a[x].maxx+=y;
			a[x].add+=y;
			return ;
		}
		plusdown(x);
		int mid=(a[x].l+a[x].r)/2;
		if(l<=mid) plus(a[x].lson,l,r,y);
		if(mid<r) plus(a[x].rson,l,r,y);
		pushup(x);
	}
	long long ans=-9223372036854775808;
	void Ask(int x,int l,int r){
		if(a[x].r<l||a[x].l>r)
			return ;
		if(l<=a[x].l&&a[x].r<=r){
			ans=a[x].maxx>ans?a[x].maxx:ans;
			return ;
		}
		coverdown(x);
		plusdown(x);
		int mid=(a[x].l+a[x].r)/2;
		if(l<=mid) Ask(a[x].lson,l,r);
		if(mid<r) Ask(a[x].rson,l,r);
		pushup(x);
	}
	int main(){
		cin>>n>>q;
		for(int i=1;i<=n;i++)
			cin>>val[i];
		Build(Root,1,n);
		while(q--){
			int op;
			cin>>op;
			if(op==1){
				int l,r,x;
				cin>>l>>r>>x;
				cover(Root,l,r,x);
			}
			else if(op==2){
				int l,r,x;
				cin>>l>>r>>x;
				plus(Root,l,r,x);
			}
			else{
				int l,r;
				cin>>l>>r;
				ans=-9223372036854775808;
				Ask(Root,l,r);
				cout<<ans<<"\n";
			}
		}
		return 0;
	}
}
signed main(){
	//freopen("P1253_7.in","r",stdin);
	//freopen("new.out","w",stdout);
	ios::sync_with_stdio(false);
	cin.tie(0);
	Tree::main();
	return 0;
}