#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("YES");}else{puts("NO");}
#define MAX_N 200005

int main() {
    ll n;
    cin >> n;
    ll a[n], b[n];
    rep(i,n)cin >> a[i];
    rep(j,n)cin >> b[j];
    int flag = 1;
    ll sum = 0;
    rep(i,n)sum += a[i] - b[i];
    if(sum < 0) flag = 0;
    if(n == 2){
        if(sum==0){
            cout << abs(a[0]-a[1]) << endl;
        }else{
            cout << -1 << endl;
        }
        return 0;
    }
    if(sum % (n-2) != 0) flag = 0;
    ll ans = sum / (n-2);
    rep(i,n)a[i] -= ans;
    rep(i,n){
        if(a[i] > b[i]){
            flag = 0;
        }else if((a[i]-b[i])%2!=0){
            flag = 0;
        }
    }
    if(flag){
        cout << ans << endl;
    }else{
        cout << -1 << endl;
    }
    return 0;
}