#include <bits/stdc++.h>

#define rep(i,s,n) for(int i = int(s); i < int(n); i++)
#define rrep(i,s,n) for(int i = int(n) - 1; i >= int(s); i--)
#define all(v) (v).begin(), (v).end()

using ll = long long;
using ld = long double;
using ull = unsigned long long;

bool chmin(auto &a, auto b) {
    if(a <= b) return false;
    a = b;
    return true;
}

bool chmax(auto &a, auto b) {
    if(a >= b) return false;
    a = b;
    return true;
}

using namespace std;

ll solve1(int m, vector<ll> a, vector<ll> b){
    ll asum = 0, bsum = 0;
    ll amax = 0, bmax = 0;
    rep(i,0,m){
        asum += a[i];
        if (a[i] > 0) chmax(amax,ll(i));
    }
    rep(i,0,m){
        bsum += b[i];
        if (b[i] > 0) chmax(bmax,ll(i));
    }
    if (amax + bmax < m){
        // cout << 0 << '\n';
        return 0;
    }
    if (asum < bsum){
        a[0] += bsum - asum;
    }
    else if (asum > bsum){
        b[0] += asum - bsum;
    }
    ll ans = 0;
    ll pre = 0;
    bool more_mp1 = false;
    bool safe = false;
    rep(i,0,m){
        if (b[i] > 0){
            if (pre > 0){
                more_mp1 = true;
            }
        }
        pre += a[m-1-i];
        if (b[i] > pre){
            if (ans > 0){
                safe = true;
            }
            ans += pre;
            pre = 0;
        }
        else if (b[i] == pre){
            ans += pre;
            pre = 0;
        }
        else {
            ans += b[i];
            pre -= b[i];
        }
    }
    if (!more_mp1 && !safe) ans--;
    // cout << ans << '\n';
    return ans;
}

void solve(){
    int m; cin >> m;
    vector<ll> a(m), b(m);
    rep(i,0,m) cin >> a[i];
    rep(j,0,m) cin >> b[j];
    ll ans1 = solve1(m,a,b);
    ll ans2 = solve1(m,b,a);
    cout << max(ans1,ans2) << '\n';
    // assert(ans1 == ans2);
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);
    int t; cin >> t;
    while (t--){
        solve();
    }
}