#include<bits/stdc++.h>
using namespace std;
#define N 1000005
#define M 998244353
#define ll long long

#define pii pair<ll,ll>
ll a[N],b[N];

int main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(NULL);
    std::cout.tie(NULL);
    ll T;
    cin>>T;
    while(T--)
    {
        ll n,mb=0,ma=0,suma=0,sumb=0;
        cin>>n;
        for(int i=0;i<n;i++)
        {
            cin>>a[i];
            suma+=a[i];
            if(a[i]) ma=i;
        }
        for(int i=0;i<n;i++)
        {
            cin>>b[i];
            sumb+=b[i];
            if(b[i]) mb=i;
        }
        if(ma+mb<n)
        {
            cout<<0<<endl;continue;
        }
        ll rest=0,ans=0,used=0,sa=0;
        for(int i=1;i<n-1;i++)
        {
            ans+=min(a[i],b[n-i-1]);
            sa+=a[i];
            if(a[i]<b[n-i-1]&&n-i-1)
            {
                b[n-i-2]+=b[n-i-1]-a[i];
               if(sa!=suma||a[n-1]) rest=1;
            }
            if(a[i]>b[n-i-1]&&(b[n-1]||used)) rest=1;
            used+=min(a[i],b[n-i-1]);
        }
        if(!rest) ans--;
        cout<<min(ans+a[n-1]+b[n-1],max(suma,sumb))<<endl;
    }
    return 0;
}