#include <bits/stdc++.h>

using std::ios;
using std::cin;
using std::cout;
typedef long long ll;
const int N = 5e5 + 5;
const int Maxn = 1e9;
int T_data, m;
ll ta, tb, a[N], b[N];

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	
	cin >> T_data;
	while (T_data--)
	{
		cin >> m;
		ta = tb = 0;		
		for (int i = 0; i < m; ++i)
			cin >> a[i], ta += a[i];
		for (int i = 0; i < m; ++i)
			cin >> b[i], tb += b[i];
		if (ta < tb)
			a[0] += tb - ta;
		if (ta > tb)
			b[0] += ta - tb;
		ll cnt0 = 0, cnt1 = 0, cnt2 = 0;
		int amin = Maxn, bmin = Maxn;
		for (int i = 0, j = m - 1; i < m; ++i)
		{
			while (j > 0 && b[j] == 0)
				--j;
			while (a[i] > 0 && b[j] > 0 && i + j >= m - 1)
			{
				ll temp = std::min(a[i], b[j]);
				a[i] -= temp;
				b[j] -= temp;
				if (i + j >= m)
					cnt0 += temp;
				else 
				{
					++cnt2;
					cnt1 += temp; 
					if (i < amin)
						amin = i;
					if (j < bmin)
						bmin = j; 
				}
				while (j > 0 && b[j] == 0)
				--j;
			}
		}
//		for (int i = 0; i < m; ++i)
//			cout << a[i] << ' ';
//		cout << '\n';
//		for (int i = 0; i < m; ++i)
//			cout << b[i] << ' ';
//		cout << '\n';
		if (cnt0 > 0)
			cout << cnt0 + cnt1 << '\n';
		else
		{
			bool flag = false; 
			for (int i = amin + 1; i < m; ++i)
				if (a[i] > 0)
				{
					flag = true;
					break ;	
				}
			for (int i = bmin + 1; i < m; ++i)
				if (b[i] > 0)
				{
					flag = true;
					break ;
				}
			if (flag)
				cout << cnt0 + cnt1 << '\n';
			else if (cnt2 > 1)
				cout << cnt0 + cnt1 - 1 << '\n';
			else 
				cout << 0 << '\n';
		}
	}	
}