#include <bits/stdc++.h>
using namespace std;

int main() {
  int n;
  cin>>n;
  long long wa_a=0;
  long long wa_b=0;
  long long sa=-1*LLONG_MAX;
  vector<long long >a(n),b(n);
  long long kotae=0;
  for(int i=0;i<n;i++){
    cin>>a[i];
    wa_a+=a[i];
  }
  for(int i=0;i<n;i++){
    cin>>b[i];
    wa_b+=b[i];
  }
  for(int i=0;i<n;i++){
    sa=max(sa,b[i]-a[i]);
  }
  if(n==2){
    if(wa_a-wa_b==0){
      cout<<sa<<endl;
      return 0;
    }else{
      cout<<-1<<endl;
      return 0;
    }
  }else if(n==3){
    if((wa_a-wa_b)%3==0&&sa>0){
      cout<<wa_a-wa_b<<endl;
      return 0;
    }else{
      cout<<-1<<endl;
      return 0;
    }
  }else if(sa*(n-2)<= wa_a-wa_b&&(wa_a-wa_b)%(n-2)==0&&sa>0){
    kotae=(wa_a-wa_b)/(n-2);
    cout<<kotae<<endl;
  }else{
    cout<<-1<<endl;
  }
  return 0;
}