#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int m;
ll a[500005],b[500005];
void solve(){
	cin >> m;
	for(int i=0; i<m ;i++) cin >> a[i];
	for(int i=0; i<m ;i++) cin >> b[i];
	{
		ll ta=0,tb=0;
		for(int i=0; i<m ;i++){
			ta+=a[i];tb+=b[i];
		}
		ll t=max(ta,tb);
		a[0]+=t-ta;
		b[0]+=t-tb;
	}
	
	ll sa=0,sb=0;
	ll res=0;
	for(int i=0; i<m ;i++){
		sa+=a[i];
		sb+=b[m-i-1];
		ll cur=min(sa,sb);
		res+=cur;
		sa-=cur;sb-=cur;
		sa=0;
	}
	ll suma=0,sumb=0;
	{
		ll frog=res;
		for(int i=m-1; i>=0 ;i--){
			ll cur=min(a[i],frog);
			frog-=cur;
			a[i]=cur;
			suma+=a[i]*i;
		}
	}
	{
		ll frog=res;
		for(int i=m-1; i>=0 ;i--){
			ll cur=min(b[i],frog);
			frog-=cur;
			b[i]=cur;
			sumb+=b[i]*i;
		}
	}
	//cout << a[0] << ' ' << a[1] << ' ' << b[0] << ' ' << b[1] << ' ' << res << endl;
	//cout << res << ' ' << suma << ' ' << sumb << endl;
	if(res==0 || suma+sumb>res*(m-1)) cout << res << '\n';
	else cout << res-1 << '\n';
}
int main(){
	ios::sync_with_stdio(false);cin.tie(0);
	int t;cin >> t;while(t--) solve();
}