#define _CRT_SECURE_NO_WARNINGS 1
#pragma warning(disable:6031)
#include<bits/stdc++.h>
using namespace std;
#define int long long
template <typename T> void read(T& x) {
	x = 0;int f = 1;char c = getchar();
	for (; !isdigit(c); c = getchar()) if (c == '-') f *= -1;
	for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - '0';
	x *= f;
}

int a[500050];
int b[500050];

void solve() {
	int m;
	read(m);
	int end1 = 0, end2 = 0;
	int sum1 = 0, sum2 = 0;
	for (int i = 0;i < m;++i) {
		read(a[i]);
		if (a[i]) end1 = i;
		sum1 += a[i];
	}
	for (int i = 0;i < m;++i) {
		read(b[i]);
		if (b[i]) end2 = i;
		sum2 += b[i];
	}

	int end22 = end2;

	if (sum1 > sum2) {
		b[0] += sum1 - sum2;
	}
	else {
		a[0] += sum2 - sum1;
	}

	int ans = 0;
	int f = 0;

	for (int i = 0;i <= end1;++i) {
		if (a[i]) {
			for (int j = end2;j >= 0;--j) {
				if (b[j] && i + j >= m - 1) {
					if (i + j > m - 1) {
						f = 1;
					}
					if (a[i] > b[j]) {
						ans += b[j];
						--end2;
						a[i] -= b[j];
					}
					else {
						ans += a[i];
						b[j] -= a[i];
						break;
					}
				}
			}
		}
	}

	if (f) {
		printf("%lld\n", ans);
	}
	else {
		if (end1 + end22 > m - 1) {
			printf("%lld\n", ans - 1);
		}
		else {
			puts("0");
		}
	}
}

signed main() {
	int t;
	read(t);
	while (t--)
		solve();
	return 0;
}