#include <bits/stdc++.h>
using namespace std;
#define int long long
const int inf = 1e7;
void solve()
{
    int m;
    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 (sum1 < sum2)
        a[0] += sum2 - sum1;
    if (sum1 > sum2)
        b[0] += sum1 - sum2;
    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] && resb)
        {
            check = 1;
            break;
        }
    }
    if (!check)
    {
        cout << 0 << endl;
        return;
    }
    resb = 0;
    for (int i = 0; i < m; i++)
    {
        if (resb)
        {
            tag = 1;
        }
        resb += b[m - 1 - i];
        int delta = min(a[i], resb);
        a[i] -= delta;
        resb -= delta;
        if (a[i] && ans)
        {
            tag = 1;
        }
        ans += delta;
    }
    if (tag)
    {
        cout << ans << endl;
    }
    else
    {
        cout << ans - 1 << endl;
    }
}
signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t;
    cin >> t;
    while (t--)
        solve();
}