// author : thembululquaUwU
// 3.9.2024

#include <bits/stdc++.h>
#define pb push_back
#define fi first
#define se second
#define endl '\n'

using namespace std;
using ll = long long;
using ii = pair <int, int>;
using vi = vector <int>;

const int MaxN = 2e5;
const int mod = 1e9 + 7;

void maxl(auto &a, auto b) {a = max(a, b);}
void minl(auto &a, auto b) {a = min(a, b);}

void solve(){
    int n; cin >> n;
    vector <ii> mou(n);
    for (int i = 0; i < n; ++ i) cin >> mou[i].fi;
    for (int i = 0; i < n; ++ i) cin >> mou[i].se;
    sort(mou.begin(), mou.end());

    int ans = 0;
    for (auto [h, p] : mou){
        p -= ans;
        if (p < h){
            cout << -1 << endl;
            return;
        }
        ans += (p - h);
    }
    cout << ans << endl;
}

int main(){
    if (fopen("pqh.inp", "r")){
        freopen("pqh.inp", "r", stdin);
        freopen("pqh.out", "w", stdout);
    }
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    int t = 1; cin >> t;
    while (t --) solve();
    return 0;
}