#include using namespace std; #define REP(i,m,n) for(int i=(m); i<(int)(n); i++) #define RREP(i,m,n) for(int i=(int)((n)-1); i>=m; i--) #define rep(i,n) REP(i,0,n) #define rrep(i,n) RREP(i,0,n) #define all(a) (a).begin(),(a).end() #define rall(a) (a).rbegin(),(a).rend() #define fi first #define se second #define debug(...) {cerr<<"[L"<<__LINE__<<"] "; _debug(__VA_ARGS__);} template string join(const vector&v, string del=", "){ stringstream s; for(auto x : v) s << del << x; return s.str().substr(del.size()); } template ostream& operator<<(ostream& o, const vector&v){ if(v.size()) o << "[" << join(v) << "]"; return o; } template ostream& operator<<(ostream& o, const vector >&vv){ int l = vv.size(); if(l){ o< ostream& operator<<(ostream& o, const pair& p){ return o << "(" << p.first << ", " << p.second << ")"; } inline void _debug(){cerr< void _debug(const First& first, const Rest&... rest){cerr< pii; typedef pair pll; typedef vector vi; typedef vector vvi; typedef vector vl; typedef vector vvl; const double PI = (1*acos(0.0)); const double EPS = 1e-9; const int INF = 0x3f3f3f3f; const ll INFL = 0x3f3f3f3f3f3f3f3fLL; const ll mod = 1e9 + 7; inline void finput(string filename) { freopen(filename.c_str(), "r", stdin); } int main(){ ios_base::sync_with_stdio(0); // finput("./input"); int n; cin >> n; vl a(n),b(n),d(n); rep(i,n) cin >> a[i]; rep(i,n) cin >> b[i]; rep(i,n) d[i] = a[i] - b[i]; ll dsum = accumulate(all(d), 0ll); if(dsum < 0){ cout << -1 << endl; }else if(n == 2){ if(dsum == 0){ cout << abs(d[0]) << endl; }else{ cout << -1 << endl; } }else{ if(dsum % (n-2) == 0){ int k = dsum / ll(n-2); bool can = true; rep(i,n) if(d[i] < -k || k < d[i]) can = false; if(can){ cout << k << endl; }else{ cout << -1 << endl; } }else{ cout << -1 << endl; } } return 0; }