/*YYC is Thinking Here*/
#include<bits/stdc++.h>
#define mids(l,r) const auto mid = (l + r) >> 1
#define lb(x) (x&-x)
#define ls (x<<1)
#define rs (ls|1)
#define int long long
#define pii pair<int,int>
#define inf 0x3f3f3f3f3f3f3f3f
using namespace std;
const int maxn = 1e5+10;
int n,x,y,z,ans,a[maxn],b[maxn];
void solve(){
	cin>>n;
	for(int i = 1;i <= n;++i) cin>>a[i];
	for(int i = 1;i <= n;++i) cin>>b[i];
	x = y = z = ans = 0;
	for(int i = 1;i <= n;++i) {
		int a = ::a[i], b = ::b[i];
		if(b == 0) {
			if(x < a) {
				int d = a - x, ad = min(z,d);
				x += d, ans += d, y += ad, z -= ad;
				// if(d <= z) x += d, y += d, z -= d, ans += d;
				// else x += d, y += z, z = 0, ans += d;
			}
		} else {
			if(a == 0) return cout<<"-1\n",void();
			x = min(x, a - 1);
			y = min(y, b - 1);
			if(a - x + y < b) { //should +
				int xmv = min(x, b - (a - x + y));
				x -= xmv, z += xmv;
				int v = b - a + x - y;
				y += v, ans += v;
			} else {
				int ymv = min(y, a - x + y - b);
				y -= ymv, z += ymv;
				int v = a - x + y - b;
				x += v, ans += v;
			}
			z = min(z, a - x - 1);
		}
	}
	cout<<ans<<'\n';
}
signed main() {
	ios::sync_with_stdio(0),cin.tie(0);
	int T;cin>>T;while(T--)solve();
}

/*
* I love it all
* Go forward,move forward !
*/