#include <bits/stdc++.h>
#define endl '\n'
using namespace std;
using i64 = long long;

void solve()
{
    int m;
    cin >> m;
    i64 sig1 = 0, sig2 = 0;
    vector<i64> a(m + 1), b(m + 1), f(m + 1), g(m + 1);
    for (int i = 0; i < m; i++)
        cin >> a[i], sig1 += a[i];
    for (int i = 0; i < m; i++)
        cin >> b[i], sig2 += b[i];
    for (int i = m - 1; i >= 0; i--)
        g[i] = g[i + 1] + b[i];

    if (sig1 > sig2)
        b[0] += sig1 - sig2;
    else
        a[0] += sig2 - sig1;

    bool exist = false;
    for (int i = m - 1; i >= 0; i--)
        if (a[i] && g[m - i])
            exist = true;
    if (!exist)
    {
        cout << "0\n";
        return;
    }

    bool flag = false;
    i64 res = 0ll;
    for (int i = 0; i < m; i++)
    {
        if (g[m - i] - res > 0)
            flag = true;
        i64 tmp = min(a[i], b[m - 1 - i] + g[m - i] - res);
        res += tmp;
    }

    if (flag)
        cout << res << endl;
    else
        cout << res - 1ll << endl;
}

int main()
{
    cin.tie(nullptr)->sync_with_stdio(false);

    int t = 1;
    cin >> t;
    while (t--)
        solve();
    return 0;
}