#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
using P = pair<ll,ll>;
const ll mod = 1e9+7;
#define ALL(x) (x).begin(),(x).end()
#define REP(i,n) for(ll (i)=0;(i)<(n);(i)++)
#define REPS(i,n) for(ll (i)=1;(i)<=(n);(i)++)
#define RREP(i,n) for(ll (i)=(n-1);(i)>=0;(i)--)
#define RREPS(i,n) for(ll (i)=(n);(i)>0;(i)--)
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define UNIQUE(v) v.erase(unique(ALL(v)),v.end());

template<class T> inline void chmin(T& a, T b){
    if (a > b){
        a = b;
    }
}

template<class T> inline void chmax(T& a, T b){
    if (a < b){
        a = b;
    }
}

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout<<fixed<<setprecision(12);
    ll N;
    cin >> N;
    ll sum = 0;
    bool ok = 1;
    vector<ll> A(N);
    vector<ll> B(N);
    REP(i,N)cin >> A[i];
    REP(i,N)cin >> B[i];
    REP(i,N)sum += A[i] - B[i];
    ll count = 0;
    ll ans = 0;
    if(N == 2){
        if(A[0] + A[1] != B[0] + B[1]){
            ok = 0;
        }else{
            ans = abs(A[0] - B[0]);
        }
        cout << (ok ? ans : -1) << "\n";
    }else{
        if(sum % (N-2) != 0){
            ok = 0;
        }else{
            count = sum / (N-2);
        }
        REP(i,N){
            if(A[i] -B[i] - count > 0)ok = 0;
            if((A[i] -B[i] - count) %2 == 1)ok = 0;
        }
        if(count < 0)ok = 0;
        cout << (ok ? count : -1) << "\n";
    }
}