#include<bits/stdc++.h>
using namespace std;
const int mod =1000000000+7;
//#define int long long
int i,j;
int pre_a[500002],pre_b[500002];
int a[500002],b[500002];
int n;
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	
	cin>>n;
	for(int i=1;i<=n;++i)
	{
		cin>>a[i];
		pre_a[i]=(pre_a[i-1]+a[i])%mod;
	}
	for(int i=1;i<=n;++i)
	{
		cin>>b[i];
		pre_b[i]=(pre_b[i-1]+b[i])%mod;
	}
	
	int ans=0;
	
	int sum_a,sum_b;
	
	for(int i=1;i<=n;i++)
	{
		(ans+=(((n+1)*pre_a[i])%mod)*pre_b[i])%=mod;
		sum_a=(sum_a+pre_a[i])%mod;
		sum_b=(sum_b+pre_b[i])%mod;
	}	
	long long toto=(sum_a%mod*sum_b%mod)%mod;
	ans=(ans-toto+mod)%mod;
	cout<<ans<<endl;
//	return 0;
	return 0;
 } 

样例测了是对的，但提交就会$\red {WA}$

求巨佬查错$qwq$

IDE : Dev-C++