#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll, ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
const ll MOD = 1000000007;
const ll INF = 1e18;
#define REP(i, n) for (int i = 0; i < n; i++)
#define ALL(v) v.begin(), v.end()

int main(){
	int n; cin >> n;
	VI aa(n), b(n); 
	REP(i,n) cin >> aa[i];
	REP(i,n) cin >> b[i];
	VI a=aa;
	bool up=0, no=0;
	ll ans=0;
	REP(i,n){
		if(aa[i]<b[i]){
			if(up){
				no=1;
				break;
			}
			ans+=b[i]-a[i];
			up=1;
			ll d=b[i]-a[i];
			REP(j,n)
				a[j]-=d;
			a[i]=b[i];
		}
	}
	if(no){
		cout << -1 << endl;
		return 0;
	}
	ll down=0;
	REP(i,n)
		down+=a[i]-b[i];
	if(n==2){
		if(down==0)
			cout << ans << endl;
		else
			cout << -1 << endl;
	}
	else{
		if(down%(n-2)==0){
			ll k=down/(n-2);
			ll kk=0;
			REP(i,n){
				if((k-(a[i]-b[i]))%2)
					no=1;
				kk+=(k-(a[i]-b[i]))/2;
			}
			if(no||kk!=k)
				cout << -1 << endl;
			else
				cout << ans+k << endl;
		}
		else
			cout << -1 << endl;
	}
	return 0;
}