#include<bits/stdc++.h>
#define REP(i,n) for(int i=0,i##_len=int(n);i<i##_len;++i)
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
#define All(x) (x).begin(),(x).end()
#define rAll(x) (x).rbegin(),(x).rend()
using namespace std;
using ll = long long;

int main(){
    int N;cin>>N;
    ll sumA=0,sumB =0;
    ll ad=0;
    vector<ll> A(N);
    REP(i,N){
        cin>>A[i];
        sumA+=A[i];
    }
    REP(i,N){
        ll b;cin>>b;
        if(b>A[i]){
            ad = max(ad,b-A[i]);
        }
        sumB+=b;
    }
    if(N==2){
        if(sumA==sumB) cout<<ad<<endl;
        else cout<<-1<<endl;
        return 0;
    }
    if((sumA-sumB)%(N-2)==0&&ad <= (sumA-sumB)/(N-2)) cout<<(sumA-sumB)/(N-2)<<endl;
    else cout<<-1<<endl;
}