#include <bits/stdc++.h>

using LL = long long;
using ld = long double;
using Pair = std::pair<int, ld>;
#define inf 1'000'000'000

void solve(const int &Case) {
    int m;
    std::cin >> m;
    std::vector<LL> a(m), b(m);
    int mx = 0;
    for (auto &x: a)std::cin >> x;
    for (auto &x: b)std::cin >> x;
    a[0] = (LL) m * 3'000'000'000;
    b[0] = (LL) m * 3'000'000'000;
    for (int i = 0; i < m; i++) {
        if (a[i] > 0)mx = i;
    }
    for (int i = m - 1; i >= 0; i--) {
        if (b[i] > 0) {
            if (i + mx < m) {
                std::cout << 0 << '\n';
                return;
            }
            else break;
        }
    }
    LL ans = 0;
    int fl = 1;
    int r = m - 1, l = 0;
    while (r >= 0 && l < m) {
        while (l + r < m - 1) {
            if (b[l] > 0 && mx + l >= m)fl = 0;
            l++;
        }
        if (a[r] > 0 && b[l] > 0 && l + r >= m)fl = 0;
        if (a[r] > b[l]) {
            a[r] -= b[l];
            ans += b[l], l++;
        }
        else if (a[r] < b[l]) {
            b[l] -= a[r];
            ans += a[r], r--;
        }
        else {
            ans += b[l], r--, l++;
        }
    }
    ans -= fl;
    std::cout << ans << '\n';
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
    int T = 1;
    std::cin >> T;
    for (int Case = 1; Case <= T; Case++)solve(Case);
    return 0;
}