//#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;

#define X first
#define Y second


const ll mod = 1000000007;
//const ll mod = 998244353;





void solve()
{
    ll n;
    cin >> n;
    vector<ll> a(n), b(n);
    for (ll i=0;i<n;i++) cin >> a[i];
    for (ll i=0;i<n;i++) cin >> b[i];
    ll Sa = 0, Sb = 0;
    for (ll i=0;i<n;i++)
    {
        Sa += a[i];
        Sb += b[i];
    }
    if (Sa>Sb) b[0] += Sa-Sb;
    else a[0] += Sb-Sa;
    vector<ll> a0 = a, b0 = b;
    ll A = 0;
    ll ok = 0;
    for (ll i=0,j=n-1;i<n;i++)
    {
        while (a[i]>0 and j>=0 and i+j>=n-1)
        {
            if (b[j]==0)
            {
                j--;
                continue;
            }
            ll D = min(a[i],b[j]);
            a[i] -= D, b[j] -= D;
            A += D;
            if (i+j>=n) ok = 1;
        }
    }
    if (ok==1)
    {
        cout << A << "\n";
        return;
    }
    if (A==0)
    {
        cout << 0 << "\n";
        return;
    }
    ll mxi = -1, mni = mod;
    for (ll w=0;w<n;w++)
    {
        if (a[w]>0) mxi = max(w,mxi);
        if (a0[w]>a[w]) mni = min(w,mni);
    }
    if (mni<mxi) ok = 1;
    mxi = -1, mni = mod;
    for (ll w=0;w<n;w++)
    {
        if (b[w]>0) mxi = max(w,mxi);
        if (b0[w]>b[w]) mni = min(w,mni);
    }
    if (mni<mxi) ok = 1;
    if (ok==0) A--;
    cout << A << "\n";
}


int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    ll T;
    T = 1;
    cin >> T;
    while (T--) solve();
}