#include "bits/stdc++.h"
using namespace std;
#define int long long
#define rep(i,n) for(int i=0;i<n;i++)
#define vi vector<int>
#define all(a) a.begin(),a.end()
typedef pair<int,int> P;
constexpr long long mod=1000000007;
constexpr long long inf=1ll<<61;
int a[100006],b[100006];
signed main(){
  int n;cin>>n;
  rep(i,n)cin>>a[i];
  rep(i,n)cin>>b[i];
  int s=0;
  rep(i,n)s+=a[i];
  rep(i,n)s-=b[i];
  if(n==2){
    if(a[0]+a[1]==b[0]+b[1]){
      cout<<abs(a[0]-b[0])<<endl;
    }
    else cout<<-1<<endl;
    return 0;
  }

  if(s<0||s%(n-2))cout<<-1<<endl;
  else{
    int k=s/(n-2);
    rep(i,n)a[i]-=k;
    int cnt=0;
    rep(i,n){
      if(a[i]>b[i]){
        cout<<-1<<endl;return 0;
      }
      else if((b[i]-a[i])&1){
        cout<<-1<<endl;return 0;
      }
      else{
        cnt+=(b[i]-a[i])/2;
      }
    }
    if(k==cnt){
      cout<<k<<endl;
    }
    else{
      cout<<-1<<endl;
    }
  }
}