#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int N=5e5+10;
int n,T;ll a[N],b[N];
int main()
{
	scanf("%d",&T);
	while(T--)
	{
		scanf("%d",&n);
		int maxx=0,maxx1=0;ll s=0,s1=0;
		for(int i=0;i<n;i++)
			scanf("%lld",&a[i]),maxx=(a[i]>0?i:maxx),s+=a[i];
		for(int i=0;i<n;i++)
			scanf("%lld",&b[i]),maxx1=(b[i]>0?i:maxx1),s1+=b[i];
		if(s<s1) a[0]+=s1-s;
		else b[0]+=s-s1;
		if(maxx+maxx1<n)
		{
			printf("0\n");
			continue;
		}
		int r=n-1,flag=1;ll ans=0;
		for(int i=0;i<n&&r>=0;)
		{
			while(r>=0&&b[r]==0) r--;
			if(i+r>=n-1&&a[i]>0)
			{
				if(i+r>=n) flag=0;
				ll tmp=min(a[i],b[r]);
				a[i]-=tmp,b[r]-=tmp;
				ans+=tmp;
			}
			else i++;
		}
		printf("%lld\n",ans-flag);
	}
}