#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef long double LD;
#define int LL
#define double LD
#define endl "\n"
typedef pair<int, int> PII;
const int N = 5e5 + 5;
const int INF = 0x3f3f3f3f;
const int inf = 0x3f3f3f3f3f3f3f3f;
const double PI = acosl(-1.0);
const double eps = 1e-8;
const int MOD = 1e9 + 7;

int a[N], b[N];
int m;
void solve()
{
    cin >> m;
    int suma = 0, sumb = 0;
    int ma = INF, mb = INF;
    for (int i = 0; i < m; i++) {
        cin >> a[i];
        suma += a[i];
        if (a[i]) ma = max(ma, i);
    }
    for (int i = 0; i < m; i++) {
        cin >> b[i];
        sumb += b[i];
        if (b[i]) mb = max(mb, i);
    }
    if (sumb > suma) {
        int mid;
        for (int i = 0; i < m; i++) {
            mid = a[i];
            a[i] = b[i];
            b[i] = mid;
        }
    }
    else {
        int f = 0;
        for (int i = 0; i < m; i++) {
            if (a[i] > b[i]) {
                f = 1;
                break;
            }
        }
        if (f) {
            int mid;
            for (int i = 0; i < m; i++) {
                mid = a[i];
                a[i] = b[i];
                b[i] = mid;
            }
        }
    }
    int ans = 0;
    int ca = -1, cb = -1;
    for (int i = 0; i < m; i++) {
        if (a[i] && b[m - i]) {
            ca = i;
            cb = m - i;
            break;
        }
    }
    if (ca == -1 && cb == -1) {
        if (ma + mb >= m) {
            ca = ma;
            cb = mb;
        }
    }
    if (ca != -1 && cb != -1) {
//        cout << ca << " " << cb << " " << endl;
        a[ca]--;
        b[cb]--;
        ans++;
    }
    else {
        cout << 0 << endl;
        return;
    }
    int r = m - 1;
    int t = m - 1;
    for (int i = 0; i < m; i++) {
        while (r >= 0 && a[i] >= b[r] && i + r >= t) {
            ans += b[r];
            a[i] -= b[r];
            r--;
        }
        if (r >= 0 && a[i] < b[r] && i + r >= t) {
            ans += a[i];
            b[r] -= a[i];
            a[i] = 0;
        }
    }
    ans += a[m-1];
//    cout << "olahfc\n";
    cout << ans << endl;
}

signed main()
{
    ios::sync_with_stdio(false), cin.tie(0);
    int _;
    cin >> _;
//    _ = 1;
    while (_--) {
        solve();
    }
    return 0;
}