#include <iostream>
#include <cstdio>
#include <vector>
#include <cmath>
#include <cstring>
#include <numeric>
#include <algorithm>
#include <functional>
#include <array>
#include <map>
#include <queue>
#include <time.h>
#include <limits.h>
#include <set>
#include <stack>
#include <random>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#define rep(i,s,n) for(int i = (s); (n) > i; i++)
#define REP(i,n) rep(i,0,n)
#define RANGE(x,a,b) (min(a,b) <= (x) && (x) <= max(a,b)) //hei
#define DUPLE(a,b,c,d) (RANGE(a,c,d) || RANGE(b,c,d) || RANGE(c,a,b) || RANGE(d,a,b))
#define INCLU(a,b,c,d) (RANGE(a,c,d) && (b,c,d))
#define PW(x) ((x)*(x))
#define ALL(x) (x).begin(), (x).end()
#define RALL(x) (x).rbegin(), (x).rend()
#define MODU 1000000007LL
#define bitcheck(a,b)   ((a >> b) & 1)
#define bitset(a,b)      ( a |= (1 << b))
#define bitunset(a,b)    (a &= ~(1 << b))
#define MP(a,b) make_pair((a),(b))
#define Manh(a,b) (abs((a).first-(b).first) + abs((a).second - ((b).second))
#define pritnf printf
#define scnaf scanf
#define itn int
#define PI 3.141592653589


#define izryt bool
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
template<typename A, size_t N, typename T>
void Fill(A(&array)[N], const T & val) {
	std::fill((T*)array, (T*)(array + N), val);
}
pll Dir[4] = {
	{ -1 ,0 },{ 0 , 1 },{ 1 ,0 },{ 0 ,-1 }
};

//[a, b)
#define Getsum(ar, a,b) (ar[b] - ar[a])
#define INF 10000000000000000LL
#define chmax(a,b) a = max(a,b)
#define chmin(a,b) a = min(a,b)

struct Edge {
	int from, to;
	ll w;
	bool operator<(const Edge& rhs) const {
		return MP(w, MP(from, to)) < MP(rhs.w, MP(rhs.from, rhs.to));
	}

};

int mod_pow(int x, int n, int mod) {
	ll res = 1;
	while (n > 0) {
		if (n & 1) res = res * x % mod;
		x = 1LL * x * x % mod;
		n >>= 1;
	}
	return res;
}

typedef vector<vector<Edge>> Graph;
template< unsigned mod >
struct RollingHash {
	vector< unsigned > hashed, power;
	unsigned base = 10007;

	inline unsigned mul(unsigned a, unsigned b) const {
		return (1LL * a * b) % mod;
	}

	RollingHash(const string& s) {
		int sz = (int)s.size();
		hashed.assign(sz + 1, 0);
		power.assign(sz + 1, 0);
		power[0] = 1;
		for (int i = 0; i < sz; i++) {
			power[i + 1] = mul(power[i], base);
			hashed[i + 1] = mul(hashed[i], base) + s[i];
			if (hashed[i + 1] >= mod) hashed[i + 1] -= mod;
		}
	}

	unsigned get(int l, int r) const {
		unsigned ret = hashed[r] + mod - mul(hashed[l], power[r - l]);
		if (ret >= mod) ret -= mod;
		return ret;
	}


	unsigned connect(unsigned h1, unsigned h2, ll h2len) const {
		unsigned ret = mul(h1, mod_pow(base, h2len, mod)) + h2;
		if (ret >= mod) ret -= mod;
		return ret;
	}

	unsigned powstr(unsigned h2, int h2len, ll ts) const {
		if (ts == 0) return 0;

		unsigned han = powstr(h2, h2len, ts / 2);

		unsigned ret = connect(han, han, h2len * (ts / 2));
		if (ts % 2)
			ret = connect(ret, h2, h2len);

		return ret;
	}

	/*unsigned powstr(unsigned h2, int h2len, ll ts) const {
		unsigned ret = 0;

		REP(i, ts)
			ret = connect(ret, h2, h2len);

		return ret;
	}*/

	int LCP(const RollingHash< mod >& b, int l1, int r1, int l2, int r2) {
		int len = min(r1 - l1, r2 - l2);
		int low = -1, high = len + 1;
		while (high - low > 1) {
			int mid = (low + high) / 2;
			if (get(l1, l1 + mid) == b.get(l2, l2 + mid)) low = mid;
			else high = mid;
		}
		return (low);
	}
};

using RH = RollingHash< 1000000007 >;

#define issel(i)  (b[(i + n)%n] - b[(i - 1 + n) % n] - b[(i + 1 + n) % n] >= a[(i + n)%n])

signed main(void) {
	int n;
	cin >> n;
	vector<ll> a(n), b(n);

	REP(i, n)
		scanf("%lld", &a[i]);
	REP(i, n)
		scanf("%lld", &b[i]);

	set<int> cand;

	REP(i, n) {
		if (issel(i))
			cand.insert(i);
	}
	ll ans = 0;

	while (cand.size()) {
		int cur = *cand.begin();
		cand.erase(cand.begin());
		ll sum = b[(cur - 1 + n) % n] + b[(cur + 1 + n) % n];
		ll t = (b[cur] - a[cur]) / sum;
		ans += t;
		b[cur] -= t * sum;
		if (issel(cur - 1))
			cand.insert((cur - 1 + n) % n);
		if (issel(cur + 1))
			cand.insert((cur + 1 + n) % n);
	}

	REP(i, n)
		if (a[i] != b[i]) {
			cout << -1 << endl;
			return 0;
		}

	cout << ans << endl;

	return 0;
}


Measured memory_bytes: 8064