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

#define N 1000000

ll i,j,k,n,t;
ll a[N+50],b[N+50],res,na,nb,sb,mxa,mxb;

int main(){
	ios::sync_with_stdio(0); cin.tie(0);
	cin>>t;
	while(t--){
		cin>>n; na=nb=0; mxa=mxb=0;
		for(i=0;i<n;i++){
			cin>>a[i]; na+=a[i];
			if(a[i])mxa=max(mxa,i);
		}
		for(i=0;i<n;i++){
			cin>>b[i]; nb+=b[i];
			if(b[i])mxb=max(mxb,i);
		}
		a[0]+=max(0ll,nb-na);
		b[0]+=max(0ll,na-nb);
		res=0; sb=0;
		
		if(mxa+mxb<n){
			cout<<"0\n"; continue;
		}
		
		j=n-1;
		for(i=0;i<n;i++){
			while(j+i>=n-1&&j>=0&&a[i]){
				//cout<<"NMSL "<<i<<' '<<j<<endl;cout<<a[i]<<' '<<b[j]<<' '<<k<<endl;
				
				if(!b[j]){
					j--; continue;
				}
				if(j+i>=n)sb=1;
				k=min(a[i],b[j]);
				
				
				res+=k;
				a[i]-=k;
				b[j]-=k;
			}
		}
		
		if(!sb)res--;
		cout<<res<<'\n';
	}
}