#include <bits/stdc++.h>

using namespace std;
using i64 = long long;

void solve() {
	int m;
	cin >> m;

	vector<int> a(m), b(m);
	for (int i = 0; i < m; ++i) {
		cin >> a[i];
	}
	for (int i = 0; i < m; ++i) {
		cin >> b[i];
	}

	int i = m - 1, j = m - 1;
	while (!a[i]) {
		--i;
	}
	while (!b[j]) {
		--j;
	}
	if (i + j < m) {
		cout << 0 << "\n";
		return;
	}

	i64 x = accumulate(a.begin(), a.end(), 0LL);
	i64 y = accumulate(b.begin(), b.end(), 0LL);
	if (x > y) {
		swap(a, b);
		swap(x, y);
	}
	a[0] += y - x;

	i64 nine = 0;
	int mxa = 0, mxb = 0;
	for (int i = 0; i < m; ++i) {
		int v = min(a[i], b[m - 1 - i]);
		if (v) {
			mxa = i;
			mxb = max(mxb, m - 1 - i);
		}
		nine += v;
		a[i] -= v;
		b[m - 1 - i] -= v;
	}

	i64 cnt = 0;
	for (int i = 1; i < m; ++i) {
		int v = min(a[i], b[m - i]);
		cnt += v;
		b[m - i] -= v;
		b[m - i - 1] += b[m - i];
	}

	if (cnt) {
		cout << nine + cnt << "\n";
	} else {
		bool exist = false;
		for (int i = 0; i < m; ++i) {
			if (a[i] && i + mxb >= m || b[i] && i + mxa >= m) {
				exist = true;
			} 
		}
		cout << nine - !exist << "\n";
	}
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	int t;
	cin >> t;

	while (t--) {
		solve();
	}

	return 0;
}