#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 sum = 0;
	for (int i = 0;i < m;++i) {
		read(a[i]);
		if (a[i]) end1 = i;
	}
	for (int i = 0;i < m;++i) {
		read(b[i]);
		if (b[i]) end2 = i;
	}
	if (end1 == 0 || end2 == 0) {
		puts("0");
		return;
	}
	if (end1 < end2) {
		for (int i = 0;i < m;++i) {
			swap(a[i], b[i]);
		}
	}

	for (int i = 0;i < m;++i) {
		sum += b[i];
	}

	a[0] = sum;

	int ans = 0;
	int temp = 0;
	for (int i = m - end1;i < m;++i) {
		if (b[i]) {
			++ans;
			--a[end1];
			--b[i];
			break;
		}
	}


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

	printf("%lld\n", ans);
}

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