#include<iostream>
#include<iomanip>
#include<cmath>
#include<string>
#include<cstring>
#include<vector>
#include<list>
#include<algorithm>
#include<map>
#include<set>
#include<queue>
#include<stack>
using namespace std;
typedef long long ll;
#define fi first
#define se second
#define mp make_pair
#define rep(i, n) for(int i=0;i<n;++i)
#define rrep(i, n) for(int i=n;i>=0;--i)
const int inf=1e9+7;
const ll mod=1e9+7;
const ll big=1e18;
const double PI=2*asin(1);

int main() {
  ll N;
  cin>>N;
  ll A[N], B[N];
  ll suma = 0, sumb = 0;
  for(ll i=0;i<N;++i) {
    cin>>A[i];
    suma += A[i];
  }
  for(ll i=0;i<N;++i) {
    cin>>B[i];
    sumb += B[i];
  }
  if(N==2) {
    if(suma!=sumb) cout<<-1<<endl;
    else cout<<abs(A[0]-B[0])<<endl;
    return 0;
  }
  if((suma-sumb)%(N-2)!=0 || suma<sumb) {
    cout<<-1<<endl;
    return 0;
  }
  ll M = (suma-sumb)/(N-2);
  ll u[N];
  bool can = true;
  ll sumu = 0;
  for(ll i=0;i<N;++i) {
    if((B[i]-A[i]+M)%2!=0) {
      can = false;
      break;
    }
    u[i] = (B[i]-A[i]+M)/2;
    if(u[i]<0 || u[i]>M) can = false;
    sumu += u[i];
  }
  if(sumu!=M) can = false;
  if(!can) {
    cout<<-1<<endl;
    return 0;
  }
  cout<<M<<endl;
}