#include <bits/stdc++.h>
#define ll long long
#define db long double
#define eb emplace_back
#define mk make_pair
#define pi pair<ll, ll>
#define fo(i, a, b) for (ll(i) = (a); (i) <= (b); (i)++)
#define fd(i, a, b) for (ll(i) = (a); (i) >= (b); (i)--)
using namespace std;
const int N = 5e5 + 10;
ll n,x;
ll check(vector<ll> a,vector<ll> b)
{
    ll res=1;
    int j=n-1; ll tmp=0;
    fo(i,0,n-1) 
    {
        while(i+j>=n-1)
        {
            while(i+j>=n-1 && !b[j]) j--;
            if(i+j<n-1) break;
            if(i+j>=n) res=0;

            if(a[i]>b[j]) {
                a[i]-=b[j];
                tmp+=b[j];
                b[j]=0;
            }
            else {
                b[j]-=a[i];
                tmp+=a[i];
                a[i]=0;
                break;
            }
            j--;
        }
    }
    // cout<<tmp<<" "<<res <<"\n";
    return tmp+a[n-1]-res;
}
vector<ll> a,b;
void solve()
{
    a.clear(),b.clear();
    cin>>n;
    fo(i,0,n-1) cin>>x,a.eb(x);
    fo(i,0,n-1) cin>>x,b.eb(x);
    cout<<max(check(a,b),check(b,a))<<"\n";
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    int T;
    cin >> T;
    while (T--)
    {
        solve();
    }
    return 0;
}