#include <bits/stdc++.h>
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define rep(i,N) for(long long i = 0; i < (long long)(N); i++)
#define repr(i,N) for(long long i = (long long)(N) - 1; i >= 0; i--)
#define rep1(i,N) for(long long i = 1; i <= (long long)(N) ; i++)
#define repr1(i,N) for(long long i = (N) ; (long long)(i) > 0 ; i--)
#define each(x,v) for(auto& x : v)
#define all(v) (v).begin(),(v).end()
#define sz(v) ((int)(v).size())
#define ini(...) int __VA_ARGS__; in(__VA_ARGS__)
#define inl(...) long long __VA_ARGS__; in(__VA_ARGS__)
#define ins(...) string __VA_ARGS__; in(__VA_ARGS__)
using namespace std; void solve();
using ll = long long; template<class T = ll> using V = vector<T>;
using vi = V<int>; using vl = V<>; using vvi = V< V<int> >;
constexpr int inf = 1001001001; constexpr ll infLL = (1LL << 61) - 1;
struct IoSetupNya {IoSetupNya() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); cerr << fixed << setprecision(7);} } iosetupnya;
template<typename T, typename U> inline bool amin(T &x, U y) { return (y < x) ? (x = y, true) : false; }
template<typename T, typename U> inline bool amax(T &x, U y) { return (x < y) ? (x = y, true) : false; }
template<typename T, typename U> ostream& operator <<(ostream& os, const pair<T, U> &p) { os << p.first << " " << p.second; return os; }
template<typename T, typename U> istream& operator >>(istream& is, pair<T, U> &p) { is >> p.first >> p.second; return is; }
template<typename T> ostream& operator <<(ostream& os, const vector<T> &v) { int s = (int)v.size(); rep(i,s) os << (i ? " " : "") << v[i]; return os; }
template<typename T> istream& operator >>(istream& is, vector<T> &v) { for(auto &x : v) is >> x; return is; }
void in(){} template <typename T,class... U> void in(T &t,U &...u){ cin >> t; in(u...);}
void out(){cout << "\n";} template <typename T,class... U> void out(const T &t,const U &...u){ cout << t; if(sizeof...(u)) cout << " "; out(u...);}
template<typename T>void die(T x){out(x); exit(0);}
#ifdef NyaanDebug
  #include "NyaanDebug.h"
  #define trc(...) do { cerr << #__VA_ARGS__ << " = "; dbg_out(__VA_ARGS__);} while(0)
  #define trca(v,N) do { cerr << #v << " = "; array_out(v , N);cout << endl;} while(0)
#else
  #define trc(...)
  #define trca(...)
  int main(){solve();}
#endif

#define in2(N,s,t) rep(i,N){in(s[i] , t[i]);}
#define in3(N,s,t,u) rep(i,N){in(s[i] , t[i] , u[i]);}
using vd = V<double>; using vs = V<string>; using vvl = V< V<> >;
template<typename T>using heap = priority_queue< T , V<T> , greater<T> >;

using P = pair<int,int>; using vp = V<P>;
constexpr int MOD = /** 1000000007; //*/ 998244353;
//////////////////

// セグ木
template<typename T,typename F>
struct ST{

  int size;
  vector<T> seg;
  const F func;
  const T UNIT;
  
  ST(int N,F func , T UNIT): func(func) , UNIT(UNIT) {
    size = 1;
    while(size < N) size <<= 1;
    seg.assign(2 * size, UNIT);
  }

  ST(const vector<T> &v,F func , T UNIT) : func(func) , UNIT(UNIT){
    // initialize
    int N = (int)v.size();
    size = 1;
    while(size < N) size <<= 1;
    seg.assign(2 * size , UNIT);
    // set
    for(int i = 0; i < N; i++){
      seg[i + size] = v[i];
    }
    build();
  }

  void set(int k, T x){
    seg[k + size] = x;
  }

  void build(){
    for(int k = size-1; k > 0; k--){
      seg[k] = func(seg[2 * k] , seg[2 * k + 1] );
    }
  }
  
  void update(int k, T x){
    k += size; seg[k] = x;
    while(k >>= 1){
      seg[k] = func( seg[2 * k] , seg[2 * k + 1] );
    }
  }

  void add(int k , T x){
    k += size; seg[k] += x;
    while(k >>= 1){
      seg[k] = func(seg[2 * k] , seg[2 * k + 1] );
    }
  }
  
  // 半開区間[a,b)へのクエリ
  T query(int a, int b){
    T L = UNIT, R = UNIT;
    for(a+=size,b+=size; a<b; a>>=1,b>>=1){
      if(a & 1) L = func(L,seg[a++]);
      if(b & 1) R = func(seg[--b],R);
    }
    return func(L, R);
  }

  T operator[](const int &k) const{
    return seg[k + size];
  }

};

void solve(){
  ini(N);
  vl a(N),b(N); in(a,b);
  auto f=[&](ll a,ll b){return max(a,b);};
  ST<ll,decltype(f)> seg(b,f,-1);
  ll ans = 0;
  auto nxt = [&](int idx){return (idx + 1) % N;};
  auto pre = [&](int idx){return (idx + N - 1) % N;};
  while(seg.query(0 , N) > 0){
    rep(i,N) trc(seg[i]);
    int idx;
    {
      int l = 0 , r = N;
      while(l + 1 < r){
        int med = (l + r) / 2;
        if(seg.query(l,med) < seg.query(med,r)) l = med;
        else r = med;
      }
      idx = l;
    }
    ll nei = b[pre(idx)] + b[nxt(idx)];
    ll val = b[idx] % nei;
    trc(idx , nei , val);
    if(val > a[idx] && val == b[idx]) die(-1); 
    if(val >= a[idx]){
      ans += b[idx] / nei;
      b[idx] = val;
      seg.update(idx , val == a[idx] ? -1 : val);
    }
    else{
      if(b[idx] % nei != a[idx] % nei) die(-1);
      ans += (b[idx] - a[idx]) / nei;
      seg.update(idx , -1);
      seg.update(pre(idx) , -1);
      seg.update(nxt(idx) , -1);
      b[idx] = a[idx];
    }
  }
  rep(i , N){
    if(a[i] != b[i]) die(-1);
  }
  out(ans);
  
}

Measured memory_bytes: 7552