70分求助！
问题知道了，无法处理负权。但是不知道怎么改啊...

#include<bits/stdc++.h>
using namespace std;
int a[1000010];
int tr[4000040];
int lz[4000040];
void build(int l,int r,int id)
{
	if(l==r)
	{
		tr[id]=a[l];
		return;
	}
	int mid=(l+r)/2;
	build(l,mid,id*2);
	build(mid+1,r,id*2+1);
	tr[id]=tr[id*2]+tr[id*2+1];
}
void upd(int lu,int ru,int ln,int rn,int id,int k)
{
	if(lu<=ln&&ru>=rn)
	{
		tr[id]+=(rn-ln+1)*k;
		lz[id]+=k;
		return;
	}
	int mid=(ln+rn)/2;
	if(lz[id]!=0&&ln!=rn)
	{
		tr[id*2]+=lz[id]*(mid-ln+1);
		tr[id*2+1]+=lz[id]*(rn-mid);
		lz[id*2]+=lz[id];
		lz[id*2+1]+=lz[id];
		lz[id]=0;
	}
	if(lu<=mid)upd(lu,ru,ln,mid,id*2,k);
	if(ru>mid)upd(lu,ru,mid+1,rn,id*2+1,k);
	tr[id]=tr[id*2]+tr[id*2+1];
}
int getsum(int lc,int rc,int ln,int rn,int id)
{
	if(lc<=ln&&rc>=rn)
	{
		return tr[id];
	}
	int mid=(ln+rn)/2;
	if(lz[id]!=0)
	{
		tr[id*2]+=lz[id]*(mid-ln+1);
		tr[id*2+1]+=lz[id]*(rn-mid);
		lz[id*2]+=lz[id];
		lz[id*2+1]+=lz[id];
		lz[id]=0;
	}
	int sum=0;
	if(lc<=mid)sum+=getsum(lc,rc,ln,mid,id*2);
	if(rc>mid)sum+=getsum(lc,rc,mid+1,rn,id*2+1);
	return sum;
}
int main()
{
	int n,m;
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	build(1,n,1);
	for(int i=1;i<=m;i++)
	{
		int op;
		cin>>op;
		if(op==1)
		{
			int x,y,k;
			cin>>x>>y>>k;
			upd(x,y,1,n,1,k);
		}
		else if(op==2)
		{
			int x,y;
			cin>>x>>y;
			cout<<getsum(x,y,1,n,1)<<endl;
		}
	}
	return 0;
}