#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <cmath>
#include <map>
#include <queue>
#include <iomanip>
#include <set>
#include <tuple>
#define mkp make_pair
#define mkt make_tuple
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define all(v) v.begin(),v.end()
using namespace std;
typedef long long ll;
const ll MOD=1e9+7;
template<class T> void chmin(T &a,const T &b){if(a>b) a=b;}
template<class T> void chmax(T &a,const T &b){if(a<b) a=b;}

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

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  int N;
  cin>>N;
  vector<ll> A(N),B(N);
  rep(i,N) cin>>A[i];
  rep(i,N) cin>>B[i];

  vector<ll> diff(N);
  rep(i,N) diff[i]=B[i]-A[i];
  ll dsum=0;
  rep(i,N) dsum+=diff[i];

  if(N==2){
    if(dsum!=0) fail();
    else cout<<abs(diff[0])<<endl;
    return 0;
  }

  if(dsum>0||abs(dsum)%(N-2)>0){
    cout<<-1<<endl;
    return 0;
  }

  ll num=abs(dsum)/(N-2);
  ll sum=0;
  for(int i=0;i<N;i++){
    if(diff[i]==0){
      if(num%2) fail();
      sum+=num/2;
    }else if(diff[i]>0){
      ll rest=num-diff[i];
      if(rest<0||rest%2) fail();
      sum+=diff[i]+rest/2;
    }else{
      ll rest=num-abs(diff[i]);
      if(rest<0||rest%2) fail();
      sum+=rest/2;
    }
  }

  if(sum==num) cout<<num<<endl;
  else fail();

  return 0;
}