#include<bits/stdc++.h>
#define int long long
#define Pa pair<int,int>
using namespace std;
const int N=2e6+10,mod=1e9+7;
int a[N],b[N],c[N],d[N];
int m;
void solve(){
    cin>>m;
    int mx=0;
    bool flag= false;
    for(int i=0;i<=m-1;i++){
        cin>>a[i];
        if(a[i]){
            mx=max(mx,i);
        }
    }
    for(int i=0;i<=m-1;i++){
        cin>>b[i];
        if(b[i]){
            if(i+mx>=m)flag= true;
        }
    }
    if(!flag){
        cout<<0<<'\n';
        return;
    }
//    int mn=1e10;
    int ans=0;
    int l=1;
    bool f= false;
    for(int i=m-2;i>=1;i--){
        while(a[i]&&l<m-1){
            while(l+i<m-1)l++;
            if(l>=m-1)break;
            int minn=min(a[i],b[l]);
            if(i+l>=m)f= true;
            a[i]-=minn;
            ans+=minn;
            b[l]-=minn;
            if(!b[l])l++;
        }
        if(l>=m-1)break;
    }
    int s1=0,s2=0;
//    for(int i=0;i<=m-1;i++)cout<<a[i]<<' ';
//    cout<<'\n';
//    for(int i=0;i<=m-1;i++)cout<<b[i]<<' ';
//    cout<<'\n';
    for(int i=0;i<m-1;i++){
        s1+=a[i];
        if(a[i]&&i>0&&b[m-1]){
            f= true;
        }
    }
    for(int i=0;i<m-1;i++){
        s2+=b[i];
        if(b[i]&&i>0&&a[m-1]){
            f= true;
        }
    }
    int mn1=min(s1,b[m-1]);
    int mn2=min(s2,a[m-1]);
    ans+=mn1+mn2;
    a[m-1]-=mn2;
    b[m-1]-=mn1;
    ans+=max(a[m-1],b[m-1]);
    if(a[m-1]&&b[m-1])f= true;
//    cout<<f<<' ';
//    cout<<ans<<' ';
    if(!f)ans--;
    cout<<ans<<'\n';
}
signed main(){
    ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    int T=1;cin>>T;
    while(T--)solve();
}
//1
//10
//5 3 5 3 2 4 2 4 1 5
//9 9 8 2 4 4 3 5 3 0
//5 1 0 0 0 0 0 0 0 5
//9 8 4 0 0 2 0 1 0 0
//23
//28