#define ll long long #define dd long double #define pub push_back #define pob pop_back #define puf push_front #define pof pop_front #define mp make_pair #define mt make_tuple #define fo(i , n) for(ll i = 0 ; i < n ; i++) #define tll tuple<ll ,ll , ll> #define pll pair<ll ,ll> #include<bits/stdc++.h> /*#include<iomanip> #include<cmath> #include<cstdio> #include<utility> #include<iostream> #include<vector> #include<string> #include<algorithm> #include<map> #include<queue> #include<set> #include<stack> #include<bitset>*/ dd pi = acos(-1) ; ll z = 1000000007 ; ll inf = 10000000000000000 ; ll p1 = 37 ; ll p2 = 53 ; ll mod1 = 202976689 ; ll mod2 = 203034253 ; ll fact[200] ; ll gdp(ll a , ll b){return (a - (a%b)) ;} ll ld(ll a , ll b){if(a < 0) return -1*gdp(abs(a) , b) ; if(a%b == 0) return a ; return (a + (b - a%b)) ;} // least number >=a divisible by b ll gd(ll a , ll b){if(a < 0) return(-1 * ld(abs(a) , b)) ; return (a - (a%b)) ;} // greatest number <= a divisible by b ll gcd(ll a , ll b){ if(b > a) return gcd(b , a) ; if(b == 0) return a ; return gcd(b , a%b) ;} ll e_gcd(ll a , ll b , ll &x , ll &y){ if(b > a) return e_gcd(b , a , y , x) ; if(b == 0){x = 1 ; y = 0 ; return a ;} ll x1 , y1 , g; g = e_gcd(b , a%b , x1 , y1) ; x = y1 ; y = (x1 - ((a/b) * y1)) ; return g ;} ll power(ll a ,ll b , ll p){if(b == 0) return 1 ; ll c = power(a , b/2 , p) ; if(b%2 == 0) return ((c*c)%p) ; else return ((((c*c)%p)*a)%p) ;} ll inverse(ll a ,ll n){return power(a , n-2 , n) ;} ll max(ll a , ll b){if(a > b) return a ; return b ;} ll min(ll a , ll b){if(a < b) return a ; return b ;} ll left(ll i){return ((2*i)+1) ;} ll right(ll i){return ((2*i) + 2) ;} ll ncr(ll n , ll r){if(n < r|| (n < 0) || (r < 0)) return 0 ; return ((((fact[n] * inverse(fact[r] , z)) % z) * inverse(fact[n-r] , z)) % z);} void swap(ll&a , ll&b){ll c = a ; a = b ; b = c ; return ;} //ios_base::sync_with_stdio(0); //cin.tie(0); cout.tie(0); using namespace std ; #include <ext/pb_ds/assoc_container.hpp> #include <ext/pb_ds/tree_policy.hpp> using namespace __gnu_pbds; #define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> // ordered_set s ; s.order_of_key(val) no. of elements strictly less than val // s.find_by_order(i) itertor to ith element (0 indexed) //__builtin_popcount(n) -> returns number of set bits in n ll seed; mt19937 rnd(seed=chrono::steady_clock::now().time_since_epoch().count()); // include bits void solve() { ll n; cin >> n ; ll a[n] , b[n] ; fo(i , n) cin >> a[i] ; fo(i , n) { cin >> b[i] ; b[i] -= a[i] ; } ll curr_ans = 0 , curr_dec = 0 ; ll prev_val = inf ; for(int i = 0 ; i < n ; i++) { ll curr_val = b[i] - curr_dec ; if(i == 0) curr_ans += curr_val ; if(curr_val < 0) { cout << -1 << endl ; return ; } if(curr_val <= prev_val) { prev_val = curr_val ; continue ; } ll to_dec = curr_val - prev_val ; curr_ans += to_dec ; curr_dec += to_dec ; } cout << curr_ans << endl ; return ; } int main() { ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0); #ifndef ONLINE_JUDGE freopen("inputf.txt" , "r" , stdin) ; freopen("outputf.txt" , "w" , stdout) ; freopen("error.txt" , "w" , stderr) ; #endif ll t = 1 ; cin >> t ; while(t--) { solve() ; } cerr << "Time : " << 1000 * ((double)clock()) / (double)CLOCKS_PER_SEC << "ms\n"; return 0; }