#include <bits/stdc++.h>  
using namespace std;  

#define int long long  

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

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

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

	reverse(b.begin(), b.end());
	int s = 0;
	int ans = 0;
	bool ok = true;
	for (int i = 0; i < m; i++) {
		if (ok && s > 0 && a[i] > 0) {
			s--;
			a[i]--;
			ans++;
			ok = false;
		}
		s += b[i];
		if (s >= a[i]) {
			s -= a[i];
			ans += a[i];
		} else {
			ans += s;
			s = 0;
		}
	}	

	cout << ans - ok << "\n";
}

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

    int t;
    cin >> t;
    while (t--) {
    	solve();
    }

    return 0;
}