#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int N = 5e5 + 5, INF = 0x3f3f3f3f;
int T, n, s1, s2, p, tmp;
ll ans, sa, sb, a[N], b[N];
set<int> s;
bool flag;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> T;
    while (T--) {
        ll mn = 1e9;
        cin >> n;
        s.clear();
        p = INF;
        sa = sb = 0;
        flag = false;
        for (int i = 0; i < n; i++) cin >> a[i], sa += a[i];
        for (int i = 0; i < n; i++) cin >> b[i], sb += b[i];
        for (int i = 0; i < n; i++) {
            if (a[i]) {
                mn = i;
                break;
            }
        }
        if (sa > sb)
            b[0] += sa - sb;
        else
            a[0] += sb - sa;
        for (int i = 0; i < n; i++)
            if (b[i]) s.insert(i);
        int mxb = 0;
        int mxa = 0;
        for (int i = 0; i < n; ++i) {
            if (b[i]) mxb = i;
            if (a[i]) mxa = i;
        }
        if (mxa + mxb < n) {
            cout << "0\n";
            continue;
        }
        ans = 0;
        for (int i = 0, j = n - 1;;) {
            while (j >= 0 && !b[j]) j--;
            if (j == -1) break;
            while (i < n && (i + j < n - 1 || (!a[i]))) i++;
            if (i == n) break;
            tmp = min(a[i], b[j]);
            a[i] -= tmp;
            b[j] -= tmp;
            ans += tmp;
            if (i + j >= n) flag = true;
        }
        for (int i = mn + 1; i < n; ++i) {
            if (a[i]) flag = 1;
        }
        if (!flag) ans--;
        cout << ans << "\n";
        // cout << "mn " << mn << '\n';
    }
    return 0;
}
/*
5
2
1 2
3 4
3
1 0 1
0 1 0
4
1 0 0 1
1 1 1 1
5
123456 114514 1919810 233333 234567
20050815 998244353 0 0 0
10
5 3 5 3 2 4 2 4 1 5
9 9 8 2 4 4 3 5 3 0

1
10
5 3 5 3 2 4 2 4 1 5
9 9 8 2 4 4 3 5 3 0
*/