#include<bits/stdc++.h>

using namespace std;

#define ff first
#define ss second
#define pb push_back

typedef long long ll;
typedef long double lf;
typedef pair< int, int > pii;

const int INF = (int) 1e9;
const int N = 3000;

int main()
{

    ios_base::sync_with_stdio( 0 );
    cin.tie( NULL );

    int t; cin >> t;
    while (t--) { 
        int m; cin >> m;
        ll ans = 0;
        vector <ll> va (m), vb (m);

        ll cn_a = 0, cn_b = 0;
        for (auto &e : va) cin >> e, cn_a += e;
        for (auto &e : vb) cin >> e, cn_b += e;

        ll mn = max(cn_a, cn_b);
        va[0] += mn - cn_a;
        vb[0] += mn - cn_b;
        
        int i = 0, j = m - 1;
        int may_m = 0;
        while (i < m && j >= 0) { 
            if ( vb[j] == 0 ) j--;
            else if ( va[i] == 0 ) i++;
            else if ( i + j < m - 1 ) i++;
            else {
                int ds = min(vb[j], va[i]);
                va[i] -= ds;
                vb[j] -= ds;
                ans += ds;
                may_m |= ( i + j >= m );
            }
        }

        ans -= (may_m == 0);
        cout << ans << '\n';
    }

    return 0;
}