#include<bits/stdc++.h>
#define endl '\n'
using i64 = long long;
using ll = long long;
using namespace std;
constexpr int N = 5e5 + 10;

int m;
void solve(){
    cin >> m;
    vector<int> a(m+1), b(m+1);
    for(int i=0; i<m; ++i)cin >> a[i];
    for(int i=0; i<m; ++i)cin >> b[i];
    a[0] = b[0] = 2e9 + 10;
    a[m] = b[m] = 0;
    auto check = [&](vector<int> a, vector<int> b){
        ll res = 0;
        int t = 0;
        auto cal = [&](){
            for(int i=m-1, j=0; i>0; --i){
                if(!a[i])continue;
                while(j < m && (i + j + t < m || !b[j]))++j;
                if(!b[j])break;
                if(t == 0){
                    t = 1;
                    ++res;
                    a[i]--, b[j]--;
                    ++i;
                    j = 0;
                    continue;
                }
                int d = min(a[i], b[j]);
                res += d;
                a[i] -= d;
                b[j] -= d;
                t = 1;
                if(a[i])++i;
            }
        };
        cal();
        cal();
        for(int i=0; i<m; ++i)swap(a[i], b[i]);
        cal();
        cal();
        if(a[m-1] && t)res += a[m-1];
        if(b[m-1] && t)res += b[m-1];
        return res;   
    };
    ll ans = check(a, b);
    int t = 1;
    ll res = 0;
    bool f = false;
    auto cal2 = [&](){
        for(int i=m-1, j=0; i>0; --i){
            if(!a[i])continue;
            while(j < m && (i + j + t < m || !b[j]))++j;
            if(!b[j])break;
            if(i + j >= m)f = true;
            int d = min(a[i], b[j]);
            res += d;
            a[i] -= d;
            b[j] -= d;
            t = 1;
            if(a[i])++i;
        }    
    };
    cal2();
    for(int i=0; i<m; ++i)swap(a[i], b[i]);
    cal2();
    if(a[m-1] && t)res += a[m-1];
    if(b[m-1] && t)res += b[m-1];
    // cout << res << ' ' << ans << endl;
    if(f){
        cout << res << endl;
    }
    else cout << ans << endl;

    
}

signed main(){
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int t = 1;
    cin >> t;
    while(t--)solve();
    return 0;
}