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

const int M=5e5+5;
ll A[M],B[M],C[M],D[M];
int m;

void solve(){
    cin>>m;
    for(int i=0; i<m; i++) cin>>A[i],C[i]=A[i];
    for(int i=0; i<m; i++) cin>>B[i],D[i]=B[i];
    A[m]=B[m]=C[m]=D[m]=0;
    ll ans=0;
    for(int i=0; i<m; i++){
        ll a=A[i],b=B[m-1-i];
        if(i==0) a=2e9;
        if(i==m-1) b=2e9;
        // cout<<"i = "<<i<<" , a = "<<a<<" , m-1-i = "<<m-1-i<<" , b = "<<b<<"\n";
        ll res=min(a,b);
        A[i]-=res; B[m-1-i]-=res;
        ans+=res;
    }
    bool flag=0,can=0;
    for(int i=1; i<m; i++){
        flag|=(B[m-i]>0);
        if(flag && A[i]>0){
            can=1;
            break;
        }
    }
    if(can){
        ll tot=0;
        for(int i=1; i<m; i++){
            tot+=B[m-i];
            ll res=min(tot,A[i]);
            tot-=res;
            ans+=res;
        }
        cout<<ans<<"\n";
    }else{
        flag=0,can=0;
        for(int i=1; i<m; i++){
            flag|=(B[m-i]>0);
            if(flag && C[i]>0){
                can=1;
                break;
            }
        }
        if(can){
            cout<<ans<<"\n";
            return;
        }
        flag=0,can=0;
        for(int i=1; i<m; i++){
            flag|=(A[m-i]>0);
            if(flag && D[i]>0){
                can=1;
                break;
            }
        }
        if(can){
            cout<<ans<<"\n";
            return;
        }
        int cnt=0;
        for(int i=0; i<m; i++){
            ll a=C[i],b=D[m-1-i];
            if(i==0) a=2e9;
            if(i==m-1) b=2e9;
            if(a&&b) cnt++;
        }
        if(cnt<=1){
            cout<<"0\n";
            return;
        }
        cout<<max(ans-1,0ll)<<"\n";
    }
    return;
}


int main(){
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    int T=1;
    cin>>T;
    while(T--) solve();
    return 0;
}