#include<bits/stdc++.h>
using namespace std;
const int MAX=5e5+5;
int m;
int a[MAX],b[MAX];
int a1[MAX],b1[MAX];
void sol(){
    cin>>m;
    for(int i=0;i<m;++i){
        cin>>a[i];
    }
    for(int i=0;i<m;++i){
        cin>>b[i];
    }

    long long ans=0;
    for(int i=1;i<m-1;++i)
        ans+=min(a[i],b[m-1-i]);
    ans+=a[m-1]+b[m-1];    
    for(int i=1;i<m-1;++i)
        a1[i]=a[i]-min(a[i],b[m-1-i]);
    for(int i=1;i<m-1;++i)
        b1[i]=b[i]-min(b[i],a[m-1-i]);
    
    a1[m-1]=b1[m-1]=0;

    long long tot=0,sum=0;
    for(int i=1;i<m-1;++i){
        sum+=b1[m-i];
        int cur=min((long long)a1[i],sum);
        tot+=cur;
        sum-=cur;
    }
    if(tot){
        ans+=tot;
        cout<<ans<<"\n";
    }
    else{
        int pa=-1;
        for(int i=m-1;i>=1;--i){
            if(a1[i]){
                pa=i;
                break;
            }
        }
        if(pa!=-1)
            for(int i=m-1;i>=1;--i){
                if(b[i]){
                    if(i+pa>=m){
                        cout<<ans<<"\n";
                        return;
                    }
                }
            }

        int pb=-1;
        for(int i=m-1;i>=1;--i){
            if(b1[i]){
                pb=i;
                break;
            }
        }
        if(pb!=-1)
            for(int i=m-1;i>=1;--i){
                if(a[i]){
                    if(i+pb>=m){
                        cout<<ans<<"\n";
                        return;
                    }
                }
            }

        pa=m-1,pb=m-1;
        while(pa>=1&&!a[pa])
            pa--;
        while(pb>=1&&!b[pb])
            pb--;
        if(pa+pb>=m){
            cout<<ans-1<<"\n";
        }
        else
            cout<<0<<"\n";
    }
}

int main(){

    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    int T;
    cin>>T;
    while(T--)
        sol();

    return 0;
}