#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

int main() {
	int N;
	cin >> N;
	vector<int> A(N), B(N);
	REP(i, N) scanf("%d", &A[i]);
	REP(i, N) scanf("%d", &B[i]);
	
	// 1 回の操作で合計が -(N - 2)
	ll suma = accumulate(ALL(A), 0ll);
	ll sumb = accumulate(ALL(B), 0ll);
	
	if (N == 2) {
		if (suma != sumb) puts("-1");
		else cout << abs(A[0] - B[0]) << endl;
		return 0;
	}
	if (suma < sumb || (suma - sumb) % (N - 2) != 0) {
		puts("-1");
		return 0;
	}
	
	int cnt = (suma - sumb) / (N - 2);
	ll ans = 0;
	REP(i, N) {
		A[i] -= cnt;
		if (A[i] > B[i] || (B[i] - A[i] & 1)) { puts("-1"); return 0; }
		ans += (B[i] - A[i]) >> 1;
	}
	
	if (ans == cnt) cout << ans << endl;
	else puts("-1");
}