/**
 *    author:  yangjl
 *    created: 2024.11.20 20:45:08
**/
#include <bits/stdc++.h>
#ifdef YJL
#include "debug.h"
#else
#define debug(...)0
#endif
using namespace std;
using ll = long long;

template<class T>
istream& operator>>(istream& is, vector<T>& v) {
    for(auto& x : v) {
        is >> x;
    }
    return is;
}

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int tt;
    cin >> tt;
    while(tt--) {
        int m;
        cin >> m;
        vector<int> a(m), b(m);
        cin >> a >> b;
        ll suma = accumulate(a.begin(), a.end(), 0ll);
        ll sumb = accumulate(b.begin(), b.end(), 0ll);
        if(suma < sumb) {
            swap(suma, sumb);
            swap(a, b);
        }

        bool carryExist = false;
        for(int i = 1, j = m - 1; i < m; ++i) {
            while(j > 1 and b[j] == 0) {
                j--;
            }
            if(a[i] > 0 and i + j >= m and b[j] > 0) {
                a[i] --;
                b[j]--;
                carryExist = true;
                break;
            }
        }
        if(!carryExist) {
            cout << "0\n";
            continue;
        }

        ll tmp = min<ll>(suma - sumb, a.back());
        a.back() -= tmp;
        int ans = tmp + 1;
        for(int i = m - 1, j = 0; i >= 0; --i) {
            int x = a[i];
            while(j < m and i + j < m - 1) {
                j++;
            }
            while(x and j < m) {
                int t = min(x, b[j]);
                ans += t;
                x -= t;
                b[j] -= t;
                if(b[j] == 0) {
                    j++;
                }
            }
        }
        cout << ans << '\n';
    }
    return 0;
}
/*


*/