#include <bits/stdc++.h> using namespace std; typedef long long ll; #define REP(i,n) for(int i=0,_n=(int)(n);i<_n;++i) #define ALL(v) (v).begin(),(v).end() #define CLR(t,v) memset(t,(v),sizeof(t)) template<class T1,class T2>ostream& operator<<(ostream& os,const pair<T1,T2>&a){return os<<"("<<a.first<<","<<a.second<< ")";} template<class T>void pv(T a,T b){for(T i=a;i!=b;++i)cout<<(*i)<<" ";cout<<endl;} 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;} ll nextLong() { ll x; scanf("%lld", &x); return x;} int main2() { int N = nextLong(); vector<ll> A(N), B(N); REP(i, N) A[i] = nextLong(); REP(i, N) B[i] = nextLong(); ll sumA = accumulate(ALL(A), 0LL); ll sumB = accumulate(ALL(B), 0LL); if (N == 2) { if (sumA != sumB) { cout << -1 << endl; } else { ll kk = 0; REP(i, N) { int d = abs(A[i] - B[i]); kk += d; } cout << kk/2 << endl; } return 0; } if ((sumA - sumB) % (N - 2) != 0) { cout << -1 << endl; return 0; } bool ng = false; ll k = (sumA - sumB) / (N-2); ll kk = 0; REP(i, N) { int d = B[i] - (A[i] - k); if (d < 0 || d % 2) { ng = true; } kk += d/2; } ng = ng || (kk != k); if (ng) cout << -1 << endl; else cout << k << endl; return 0; } int main() { #ifdef LOCAL for (;!cin.eof();cin>>ws) #endif main2(); return 0; }