#include <bits/stdc++.h>
using namespace std;
#define ll long long

const int N=500050;
int p[N];
ll a[N],b[N];
const ll inf=1e16;
int Find(int x){return p[x]==x?x:p[x]=Find(p[x]);}
bool was[N];
int main(){
	int t;
	scanf("%i",&t);
	while(t--){
		int m;
		scanf("%i",&m);
		for(int i=0;i<=m;i++)p[i]=i,was[i]=false;
		for(int i=0;i<m;i++){
			scanf("%lld",&a[i]);
			//if(i==0)a[i]=inf;
			if(a[i]==0)p[i]=i+1;
		}
		ll ans=0;
		bool large=false;
		for(int i=0;i<m;i++){
			scanf("%lld",&b[i]);
			//if(i==0)b[i]=inf;
			while(b[i]>0){
				int j=Find(m-1-i);
				if(j==m)break;
				ll take=min(a[j],b[i]);
				b[i]-=take;
				a[j]-=take;
				ans+=take;
				if(i+j>=m)large=true;
				was[i]=true;
				if(a[j]==0)p[j]=j+1;
			}
		}
		bool A0=true,B0=true;
		for(int i=0;i<m;i++){
			if(a[i]!=0)A0=false;
			if(b[i]!=0)B0=false;
		}
		if(A0){
			ans+=b[m-1];
			b[m-1]=0;
		}
		if(B0){
			ans+=a[m-1];
			a[m-1]=0;
		}

		if(large||ans==0)printf("%lld\n",ans);
		else{
			int mn=m,mx=-1;
			for(int i=0;i<m;i++){
				if(was[i]){
					mn=min(mn,i);
					mx=max(mx,i);
				}
			}
			bool ok1=false;
			bool ok2=mn!=mx;
			for(int i=0;i<m;i++){
				if(a[i]>0&&i+mx>=m)ok1=true;
				if(b[i]>0&&i+m-1-mn>=m)ok1=true;
			}
			if(ok1)printf("%lld\n",ans);
			else if(ok2)printf("%lld\n",ans-1);
			else printf("0\n");
		}
	}
	return 0;
}