#include <bits/stdc++.h>
using namespace std;
#define int long long
const int inf = 1e7;
int m;
int testcase = 0;
int did(vector<int> a, vector<int> b)
{
    bool tag = 0;
    int resb = 0;
    int ans = 0;
    bool check = 0;
    for (int i = 1; i < m; i++)
    {
        resb += b[m - i];
        if (a[i] != 0 && resb != 0)
        {
            check = 1;
            break;
        }
    }
    if (!check)
    {
        return 0;
    }
    resb = 0;
    for (int i = 0; i < m; i++)
    {
        if (resb != 0)
        {
            tag = 1;
        }
        resb += b[m - 1 - i];
        int delta = min(a[i], resb);
        a[i] -= delta;
        resb -= delta;
        if (a[i] != 0 && ans != 0)
        {
            tag = 1;
        }
        ans += delta;
    }
    if (tag)
    {
        return ans;
    }
    else
    {
        return ans - 1;
    }
}
void solve()
{
    testcase++;
    cin >> m;
    vector<int> a(m), b(m);
    int sum1 = 0, sum2 = 0;
    for (auto &x : a)
        cin >> x, sum1 += x;
    for (auto &x : b)
        cin >> x, sum2 += x;

    if (testcase == 51)
    {
        cout << m << endl;
        for (auto &x : a)
            cout << x << " ";
        cout << endl;
        for (auto &x : b)
            cout << x << " ";
        cout << endl;
    }

    if (sum1 < sum2)
        a[0] += sum2 - sum1;
    if (sum1 > sum2)
        b[0] += sum1 - sum2;
    cout << max(did(a, b), did(b, a)) << endl;
}
signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t;
    cin >> t;
    while (t--)
        solve();
}