#include<bits/stdc++.h>
#define endl "\n"
#define int long long
using namespace std;
using ll = long long;
const int maxn = 5e5 + 10;
int n,a[maxn],b[maxn];
void solve(void)
{
    cin>>n;
    int suma=0,sumb=0;
    for(int i=0;i<n;i++)
    {
        cin>>a[i];
        suma+=a[i];
    }
    for(int i=0;i<n;i++)
    {
        cin>>b[i];
        sumb+=b[i];
    }
    if(suma>sumb)b[0]+=suma-sumb;
    else a[0]+=sumb-suma;
    int mxa=n-1,mxb=n-1,mia=0,mib=0;
    while(mxa>=0&&!a[mxa])mxa--;
    while(mxb>=0&&!b[mxb])mxb--;
    if(mxa+mxb<n)
    {
        cout<<"0\n";
        return;
    }
    int ans1=0;
    for(int i=0;i<n;i++)
    {
        int t=min(a[i],b[n-i-1]);
        if(t)
        {
            mia=min(i,mia);
            mib=n-i-1;
        }
        ans1+=t;
        a[i]-=t;
        b[n-i-1]-=t;
    }
    int sum=0,ans2=0;
    for(int i=0;i<n;i++)
    {
        sum+=b[n-i-1];
        int t=min(a[i],sum);
        ans2+=t;
        sum-=t;
    }
    if(ans2)
    {
        cout<<ans1+ans2<<'\n';
        return;
    }
    mxa=mxb=n-1;
    while(mxa>=0&&!a[mxa])mxa--;
    while(mxb>=0&&!b[mxb])mxb--;
    int ans=ans1+ans2;
    if(mxa>mia||mxb>mib)
    {
        cout<<ans<<'\n';
        return;
    }
    cout<<ans-1<<'\n';
}
signed main(void)
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int t;
    cin>>t;
    while(t--)
    {
        solve();
    }
    return 0;
}
/*
1
10
0 0 3 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 3 3
*/