#include <bits/stdc++.h>

using namespace std;

using ll = long long;
#define int ll

#define fi first
#define se second
#define pb push_back

pair<int, bool> cnt(int m, int s, const vector<int>& a, const vector<int>& b)
{
    int ans = 0;
    int carry = 0;

    int canona = 0;
    int canonb = 0;

    for (int i=m+1; i>=-1; i--)
    {
        if (carry > 0)
            canona = 1;

        if (i>=0 && i<m)
            carry += a[i];
        if (s-i >= 0 && s-i < m)
        {
            int r = min(carry, b[s-i]);
            if (r > 0 && canona > 0)
                canona = 2;
            if (r < b[s-i] && canonb > 0)
                canonb = 2;
            if (r > 0 && canonb == 0)
                canonb = 1;
            carry -= r;
            ans += r;
        }
    }
    return {ans, canona==2 || canonb==2};
}

void solve()
{
    int m;
    cin>>m;
    vector<int> a(m);
    vector<int> b(m);
    for (int& i : a)
        cin>>i;
    a[0] = 1e18;
    for (int& i : b)
        cin>>i;
    b[0] = 1e18;

    auto c = cnt(m, m, a, b);
    if (c.fi == 0)
    {
        cout<<"0\n";
        return;
    }
    c = cnt(m, m-1, a, b);
    if (!c.se)
        c.fi--;
    cout<<c.fi<<"\n";
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);


    int T;
    cin>>T;
    while (T--)
        solve();
}