#include<bits/stdc++.h> 
using namespace std;
typedef long long ll;
template<typename T1,typename T2> bool chmin(T1 &a,T2 b){if(a<=b)return 0; a=b; return 1;}
template<typename T1,typename T2> bool chmax(T1 &a,T2 b){if(a>=b)return 0; a=b; return 1;}
int dx[4]={0,1,-1,0};
int dy[4]={1,0,0,-1};


signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(20);

    int n;
    cin>>n;
    ll a[n],b[n];
    ll sum = 0;
    for(int i=0;i<n;i++){
        cin>>a[i];
        sum += a[i];
    }
    for(int i=0;i<n;i++){
        cin>>b[i];
        sum -= b[i];
    }
    if(n == 2){
        if(a[0] >= b[0] && a[1]<=b[1] && a[0]-b[0] == b[1]-a[1])cout << b[1] - a[1] << endl;
        else if(a[0] <= b[0] && a[1] >= b[1] && a[1]-b[1] == b[0]-a[0])cout << b[0] - a[0] << endl;
        else cout << -1 << endl;
        return 0;
    }
    // sum -= (n-2)*k
    if(sum % (n-2)){
        cout << "-1\n";
        return 0;
    }
    ll now = 0;
    int cnt = 0;
    bool pos = 1;
    for(int i=0;i<n;i++){
        if(a[i] < b[i]){
            now += b[i]-a[i];
            cnt++;
        }
    }
    if(cnt > 1 || now>sum/(n-2))cout << -1 << endl;
    else cout << sum / (n-2) << endl;
}