RT

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N = 1e6+100;
struct node{
	LL l,r;
	LL maxn,add,num;
}tr[N<<2];
int a[N];
int n,q;
void pushup(int u){
	tr[u].maxn = max(tr[u<<1].maxn,tr[u<<1|1].maxn);
}
void coverpushdown(int u){
	if(tr[u].num != 0x3f3f3f3f){
		tr[u<<1].add = tr[u<<1|1].add = 0;
		tr[u<<1].maxn = tr[u<<1|1].maxn = tr[u].maxn;
		tr[u<<1].num = tr[u<<1|1].num = tr[u].num;
		tr[u].num = 0x3f3f3f3f;
	}
}
void addpushdown(int u){
	if(tr[u].add){
		coverpushdown(u);
		tr[u<<1|1].maxn += tr[u].add;
		tr[u<<1|1].maxn += tr[u].add;
		tr[u<<1].add += tr[u].add;
		tr[u<<1|1].add += tr[u].add;
		tr[u].add = 0;
	}
}
void pushdown(int u){
	coverpushdown(u);
	addpushdown(u);
}
void build(int u,int l,int r){
	if(l == r){
		tr[u] = {l,l,a[l],0,0x3f3f3f3f};
	}else{
		tr[u] = {l,r,0,0,0x3f3f3f3f};
		int mid = l+r>>1;
		build(u<<1,l,mid);
		build(u<<1|1,mid+1,r);
		pushup(u);
	}
}
void modify(int u,int l,int r,int add){
	if(tr[u].l >= l && tr[u].r <= r){
		coverpushdown(u);
		tr[u].maxn += add;
		tr[u].add += add;
	}else{
		pushdown(u);
		int mid = tr[u].l+tr[u].r>>1;
		if(l <= mid)	modify(u<<1,l,mid,add);
		if(r > mid)	modify(u<<1|1,mid+1,r,add);
		pushup(u);
	}
}
void change(int u,int l,int r,int k){
	if(tr[u].l >= l && tr[u].r <= r){
		tr[u].maxn = k;
		tr[u].add = 0;
		tr[u].num = k;
	}else{
		pushdown(u);
		int mid = tr[u].l+tr[u].r>>1;
		if(l <= mid)	modify(u<<1,l,mid,k);
		if(r > mid)	modify(u<<1|1,mid+1,r,k);
		pushup(u);
	}
}
LL query(int u,int l,int r){
	if(tr[u].l >= l && tr[u].r <= r){
		return tr[u].maxn;
	}else{
		pushdown(u);
		int mid = tr[u].l+tr[u].r>>1;
		LL ans = -0x3f3f3f3f;
		if(l <= mid)	ans = max(ans,query(u<<1,l,mid));
		if(r > mid)	ans = max(ans,query(u<<1|1,mid+1,r));
	}
}
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	
	cin >> n >> q;
	for(int i = 1;i <= n;i++){
		cin >> a[i];
	}
	build(1,1,n);
	while(q--){
		int op,x,y,z;
		cin >> op >> x >> y;
		if(op == 1){
			cin >> z;
			change(1,x,y,z);
		}else if(op == 2){
			cin >> z;
			modify(1,x,y,z);
		}else{
			cout << query(1,x,y) << endl;
		}
	}
	
	return 0;
}