#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<vector>
#include<map>
#include<set>
#include<string>
#include<queue>
#include<stack>
#include<complex>
using namespace std;
#define MOD 1000000007
#define MOD2 998244353
#define INF (1<<29)
#define LINF (1LL<<60)
#define EPS (1e-10)
#define PI 3.1415926535897932384626433832795028
typedef long long Int;
typedef pair<Int, Int> P;
typedef long double Real;
typedef complex<Real> CP;


void ok(){
    cout << "Yes" << endl;
    exit(0);
}

void ng(){
    cout <<  "-1" << endl;
    exit(0);
}

Int n;
Int a[110000], b[110000];
Int ans;
int main(){
    cin >> n;
    Int suma = 0, sumb = 0;
    for(int i = 0;i < n;i++){cin >> a[i];suma += a[i];}
    for(int i = 0;i < n;i++){cin >> b[i];sumb += b[i];}
    if(n == 2){
        if(suma != sumb)ng();
        cout << abs(a[0] - b[0]) << endl;
        return 0;
    }
    if((suma - sumb) % (n-2) != 0)ng();
    if(suma < sumb)ng();
    int cnt = (suma - sumb) / (n-2);
    for(int i = 0;i < n;i++){
        int dif = b[i] - (a[i] - cnt);
        if(dif % 2 == 1)ng();
        ans += dif / 2;
    }
    cout << ans << endl;
    
    return 0;
}