#include<iostream>
#include<cstring>
#include<vector>
using namespace std;
using LL = long long;

int main(){

#ifdef LOCAL
    freopen("data.in", "r", stdin);
    freopen("data.out", "w", stdout);
#endif

    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);

    int T;
    cin >> T;
    while(T--){
        int n;
        cin >> n;
        vector<int> a(n), b(n);
        int mx1 = 0, mx2 = 0;
        for(int i = 0; i < n; i++){
            cin >> a[i];
            if (a[i]) mx1 = i;
        }
        for(int i = 0; i < n; i++){
            cin >> b[i];
            if (b[i]) mx2 = i;
        }
        if (mx1 + mx2 < n){
            cout << 0 << '\n';
            continue;
        }
        a[0] = b[0] = 1e9;
        {
            auto c = a, d = b;
            LL ans = 0;
            int mn1 = n, mn2 = n;
            for(int i = 0; i < n; i++){
                int t = min(c[i], d[n - 1 - i]);
                if (t){
                    ans += t;
                    mn1 = min(mn1, i);
                    mn2 = min(mn2, n - 1 - i);
                    c[i] -= t;
                    d[n - 1 - i] -= t;
                }
            }
            bool flag = false;
            for(int i = mn1 + 1; i < n; i++){
                if (c[i]){
                    flag = true;
                }
            }
            for(int i = mn2 + 1; i < n; i++){
                if (d[i]){
                    flag = true;
                }
            }
            if (!flag){
                cout << ans - 1 << '\n';
                continue;
            }
        }
        // 可以完全匹配的情况.
        LL ans = 0;
        for(int i = 0, j = n - 1; i < n; i++){
            while(a[i] > 0){
                while(j >= 0 && b[j] == 0) j--;
                if (j < 0 || i + j < n - 1) break;
                int t = min(a[i], b[j]);
                ans += t;
                a[i] -= t; b[j] -= t;
            }
        }
        cout << ans << '\n';
    }

}