#include <bits/stdc++.h>
using namespace std;
#include <math.h>
#include <iomanip>
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF=1001001001;
vector<pair<int64_t,int64_t>>prime_factorize(int64_t x){
  vector<pair<int64_t,int64_t>>p;
  for(int64_t i=2;i*i<=x;i++){
    int cnt=0;
    if(x%i==0){
    while(x%i==0){cnt++;x/=i;}
    p.push_back(make_pair(i,cnt));
    }
  }
  if(x!=1){p.push_back(make_pair(x,1));}
  return p; 
}

int main() {
  int N;
  cin>>N;
  vector<int>A(N),B(N);
  int64_t sa=0;
  for(int i=0;i<N;i++){
    cin>>A[i];
    sa+=A[i];
  }
  int64_t sb=0;
  for(int i=0;i<N;i++){
    cin>>B[i];
    sb+=B[i];
  }
  if(N>=3&&sa>=sb&&(sa-sb)%(N-2)==0){
    int64_t t=(sa-sb)/(N-2);
    bool ok=true;
    for(int i=0;i<N;i++){
      int64_t q=abs(A[i]-B[i]);
      if(t<q&&(q-t)%2!=0){ok=false;}
    }
    if(ok){cout<<t<<endl;}
    else{cout<<-1<<endl;}
  }
  else if(N==2&&sa==sb){
    cout<<A[0]-B[0]<<endl;
  }
  else{cout<<-1<<endl;}
  return 0;
}