#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int T;
    cin >> T;
    while (T--) {
        int n;
        cin >> n;
        vector<long long> a(n+1), b(n+1);

        for (int i = 1; i <= n; i++) cin >> a[i];
        for (int i = 1; i <= n; i++) cin >> b[i];

        vector<long long> dp0(n+2, 0), dp1(n+2, 0);

        for (int i = n; i >= 1; i--) {
            
            dp0[i] = max(dp0[i+1], -a[i] + dp1[i+1]);

            
            dp1[i] = max(dp1[i+1], b[i] + dp0[i+1]);
        }

        cout << dp0[1] << "\n";
    }

    return 0;
}