#include<iostream>
using namespace std;
int a[500005], b[500005];
bool flag = 0,flag1=0;
int m;
int xiaochu(int front, int back) {
    long long int sum = 0;
    if (a[back] > 0 && b[front] >= 0 && front < m && a[back] > b[front]) {
        a[back] -= b[front];
        sum += b[front];
        b[front] = 0;if (front + back >= m&&b[front]!=0)flag1 = 1;
        sum += xiaochu(front + 1, back);
    }
    if (a[back] > 0 && b[front] > 0 && a[back] <= b[front]) {
        b[front] -= a[back];
        sum += a[back];if (front + back >= m)flag1 = 1;
        a[back] = 0;
    }
    //cout<<sum<<' ';
    return sum;
}
void solve() {
    long long int num = 0, na = 0, nb = 0;
    flag = 0;
    flag1 = 0;
    cin >> m;
    for (int i = 0;i < m;i++) {
        cin >> a[i];
        na += a[i];
    }
    for (int i = 0;i < m;i++) {
        cin >> b[i];
        nb += b[i];
    }
    b[m] = 0;
    a[m] = 0;
    int numa, numb;
    for (int i = m;i > 0;i--) {
        if (a[i]) {
            numa = i;
            break;
        }
    }
    for (int i = m;i > 0;i--) {
        if (b[i]) {
            numb = i;
            break;
        }
    }
    if (numa + numb < m) {
        cout << 0 << endl;
        return;
    }
    if (na > nb) {
        b[0] += na - nb;
    }
    else {
        a[0] += nb - na;
    }
    for (int i = m - 1;i >= 1;i--) {
        if (a[i] > 0 && b[m - i] > 0) {
            a[i]--;
            b[m - i]--;

            num += 1;
            flag = 1;
            // cout<<"flag="<<flag<<endl;
            break;
        }
    }
    for (int i = m - 1;i >= 0;i--) {
        int u;u = xiaochu(m - i - 1, i);
        num += u;
        // cout<<"u="<<u<<' ';
    }
    // cout << flag1 << endl;
    if (!flag && num > 0 && !flag1) {
        cout << num - 1 << endl;
    }
    else {
        cout << num << endl;
    }
}
int main() {
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
}