#include<bits/stdc++.h>
#define lowbit(x) (x & (-x))
#define endl "\n"
#define ll long long
#define int long long
using namespace std;
#define pii pair<int, int>
#define rep(i, a, b) for(int i = a; i <= b; i ++ )
#define pre(i, a, b) for(int i = a; i >= b; i -- )
#define IOS ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
const int N = 1e6 + 10;
int n, m, k;
int a[N], b[N];
void solve()
{
    cin >> n;
    int s1 = 0, s2 = 0;
    rep(i, 0, n - 1) cin >> a[i], s1 += a[i];
    rep(i, 0, n - 1) cin >> b[i], s2 += b[i];
    if(s1 < s2) a[0] += (s2 - s1);
    else b[0] += (s1 - s2);
    int ma1 = 0, ma2 = 0;
    rep(i, 0, n - 1)
    {
        if(a[i]) ma1 = i;
        if(b[i]) ma2 = i;
    }
    if(ma1 + ma2 < n)
    {
        cout << 0 << endl;
        return;
    }
    int r = n - 1, cnt = 0, f = 0;
    vector<int>v;
    rep(i, 0, n - 1)
    {
        if(!a[i]) continue;
        if(i + r < n - 1) continue;
        if(r >= 0 && !b[r]) r -- ;
        while(a[i] && r >= 0 && i + r >= n - 1)
        {
            if(r + i >= n && b[r])
            {
                f = 1;
            }
            if(b[r] <= a[i]) a[i] -= b[r], cnt += b[r], r -- , v.push_back(i);
            else
            {
                cnt += a[i];
                b[r] -= a[i];
                a[i] = 0;
                v.push_back(i);
            }
        }
    }
    vector<int>st;
    rep(i, 0, n - 1)
    {
        if(a[i]) st.push_back(i);
    }
    v.erase(unique(v.begin(), v.end()), v.end());
    for(auto it : v)
    {
        auto itt = upper_bound(st.begin(), st.end(), it);
        if(itt != st.end()) f = 1;
    }
    if(f) cout << cnt << endl;
    else cout << cnt - 1 << endl;
}
signed main()
{
    IOS;
    int _;
    _ = 1;
    cin >> _;
    while(_ -- )
    {
        solve();
    }
	return 0;
}