#pragma GCC optimize(2)
#include <bits/stdc++.h>
typedef long long ll;
using namespace std;

ll m, a[500005], b[500005];
bool fuck[500005];

void solve(){
	cin >> m;
	ll s1 = 0, s2 = 0;
	for(int i = 0; i < m; ++i) {
		cin >> a[i];
		s1 += a[i];
	}
	for(int i = 0; i < m; ++i) {
		cin >> b[i];
		s2 += b[i];
	}
	if(s1 > s2) {
		for(int i = 0; i < m; ++i) {
			swap(a[i], b[i]);
		}
	}
	for(int i = 0; i < m; ++i) fuck[i] = a[i] > 0;
	int last = -1;
	bool ok = 0;
	for(int i = 1; i < m; ++i) {
		if(b[m - i] > 0) last = m - i;
		if(a[i] == 0) continue;
		if(last != -1) { 
			ok = 1;
		}
	}
	if(!ok) {
		cout << 0 << '\n';
		return;
	}
	ll res = 0;
	for(int i = 0; i < m; ++i) {
		int j = m - i - 1;
		int tmp = min(a[i], b[j]);
		res += tmp;
		a[i] -= tmp;
		b[j] -= tmp;
	}
	ok = 0;
	bool dmm = 0;
	last = m;
	int add = 0;
	for(int i = 1; i < m; ++i) {
		if(b[m - i] > 0) last = m - i;
		if((fuck[i] & (last != m))) {
			ok = 1;
			--b[last];
			if(a[i] > 0) {
				--a[i];add = 1;
			}
			break;
		}
	}
	if(!ok) {
		cout << res - 1 << '\n';
	}
	else {
		ll sum = 0, ress = 0;
		for(int i = 1; i < m; ++i) {
			sum += b[m - i - 1];
			ll tmp = min(sum, a[i]);
			ress += tmp;
			sum -= tmp;
		}
		cout << ress + res + b[m - 1] + add << '\n';
	}
}

int main(){
    std::ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int T;cin>>T;while(T--)
	solve();
    return 0;
}