一直10分，莫名WA

#include <bits/stdc++.h> 
using namespace std;
const int N=1e6+10,inf=0x3f3f3f3f;

struct node{
	int maxx,l,r;
	int add,change;
}tr[N*4];
int a[N];

inline void pushup(int x){
	tr[x].maxx=max(tr[x*2].maxx,tr[x*2+1].maxx);
}
inline void pushdown(int x){
	if(tr[x].change!=inf){
		tr[x*2].change=tr[x].change;
		tr[x*2+1].change=tr[x].change;
		tr[x].maxx=tr[x].change;
		tr[x].change=inf;
	}
	else if(tr[x].add){
		tr[x*2].add=tr[x].add;
		tr[x*2+1].add=tr[x].add;
		tr[x].maxx+=tr[x].add;
	}
	tr[x].add=0;
}

void build(int x,int l,int r){
	tr[x].l=l,tr[x].r=r;
	tr[x].add=0,tr[x].change=inf;
	if(l==r){
		tr[x].maxx=a[l];
		return;
	}
	int mid=(l+r)/2;
	build(x*2,l,mid),build(x*2+1,mid+1,r);
	pushup(x);
}
int query(int x,int l,int r){
	pushdown(x);
	if(l<=tr[x].l&&r>=tr[x].r) return tr[x].maxx;
	int mid=(tr[x].l+tr[x].r)/2,maxx=-inf;
	if(l<=mid) maxx=query(x*2,l,r);
	if(r>mid) maxx=max(maxx,query(x*2+1,l,r));
	return maxx;
}
void change(int x,int l,int r,int k){
	pushdown(x);
	if(l<=tr[x].l&&r>=tr[x].r) tr[x].change=k;
	else{
		int mid=(tr[x].l+tr[x].r)/2;
		if(l<=mid) change(x*2,l,r,k);
		if(r>mid) change(x*2+1,l,r,k);
	}
	pushup(x);
}

void add(int x,int l,int r,int k){
	pushdown(x);
	if(l<=tr[x].l&&r>=tr[x].r) tr[x].add+=k;
	else{
		int mid=(tr[x].l+tr[x].r)/2;
		if(l<=mid) change(x*2,l,r,k);
		if(r>mid) change(x*2+1,l,r,k);
	}
	pushup(x);
}
int n,q;
int main(){
	cin>>n>>q;
	for(int i=1;i<=n;i++) cin>>a[i];
	build(1,1,n);
	while(q--){
		int op,l,r,x;
		cin>>op>>l>>r;
		switch(op){
		case 1:
			cin>>x;
			change(1,l,r,x);
			break;
		case 2:
			cin>>x;
			add(1,l,r,x);
			break;
		case 3:
			cout<<query(1,l,r)<<endl;
			break;
		}
	}
}