#include <iostream>

using namespace std;
const int N = 5e5+100;

int a[N], b[N], c[N];
int n;
using ll = long long;

void sol() {
    cin >> n;
    ll suma = 0, sumb = 0;
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
        suma += a[i];
    }
    for (int i = 0; i < n; ++i) {
        cin >> b[i];
        c[i] = (b[i] > 0);
        sumb += b[i];
    }
    if (suma > sumb) {
        b[0] += suma - sumb;
    } else if (sumb > suma) {
        a[0] += sumb - suma;
    }
    for (int i = n - 1; i >= 0; --i) {
        c[i] |= c[i + 1];
    }
    bool flag = 0;
    for (int i = 1; i < n; ++i) {
        if (c[n - i] > 0) {
            flag = 1;
            break;
        }
    }
    if (flag == 0) {
        cout << 0 << '\n';
        return;
    }
    ll cnta = 0, cntb = 0, ans = 0;
    flag = 0;
    for (int i = 0; i < n; ++i) {
        if (cntb > 0 && a[i] > 0) {
            flag = 1;
        }
        cnta = a[i];
        cntb += b[n - 1 - i];
        ll tmp = min(cnta, cntb);
        ans += tmp;
        cnta -= tmp;
        cntb -= tmp;
    }
    if (!flag) {
        ans -= 1;
    }
    cout << ans << '\n';
}

int main() {
    ios::sync_with_stdio(0);
    int T;
    cin >> T;
    while(T --) {
        sol();
    }
    return 0;
}