#include <bits/stdc++.h> using namespace std; using ll=long long; using ld=long double; const ll ILL=2167167167167167167; const int INF=2100000000; #define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++) #define all(p) p.begin(),p.end() template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>; template<class T> int LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();} template<class T> int UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();} template<class T> bool chmin(T &a,T b){if(b<a){a=b;return 1;}else return 0;} template<class T> bool chmax(T &a,T b){if(a<b){a=b;return 1;}else return 0;} template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());} template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});} bool yneos(bool a,bool upp=false){if(a){cout<<(upp?"YES\n":"Yes\n");}else{cout<<(upp?"NO\n":"No\n");}return a;} template<class T> void vec_out(vector<T> &p,int ty=0){ if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'<<p[i]<<'"';}cout<<"}\n";} else{if(ty==1){cout<<p.size()<<"\n";}for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}} template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;} template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;} template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;} int pop_count(long long a){int res=0;while(a){res+=(a&1),a>>=1;}return res;} struct point{ ll x; ll y; }; void solve(); // CITRUS CURIO CITY / FREDERIC int main() { ios::sync_with_stdio(false); cin.tie(nullptr); int t = 1; // cin >> t; rep(i, 0, t) solve(); } void solve(){ int N; cin >> N; vector<point> p(N); rep(i, 0, N){ cin >> p[i].x >> p[i].y; } rep(i, 0, N) p.push_back(p[i]); auto f = [&](point a, point b, point c) -> int { ll A = a.y - b.y; ll B = b.x - a.x; ll C = -(A * a.x + B * a.y); assert(A * b.x + B * b.y + C == 0); ll res = A * c.x + B * c.y + C; if (res < 0) return -1; if (res > 0) return 1; return 0; }; rep(i, 0, N){ // 同一直線上 if (f(p[i], p[i + 1], p[i + 2]) == 0){ cout << "0\n"; return; } // 自己交差 rep(j, 2, N - 1){ int a = f(p[i], p[i + 1], p[i + j]); int b = f(p[i], p[i + 1], p[i + j + 1]); int c = f(p[i + j], p[i + j + 1], p[i]); int d = f(p[i + j], p[i + j + 1], p[i + 1]); if (a != b && c != d){ cout << "0\n"; return; } } } // Yes rep(rp, 0, 2){ reverse(all(p)); rep(i, 0, N){ rep(j, 0, N) if (i != j){ p[j].x -= p[i].x; p[j].y -= p[i].y; } p[i].x = 0, p[i].y = 0; vector<int> order; rep(j, 0, N) if (j != i) order.push_back(j); sort(all(order), [&](int l, int r){ if (l == r) return false; if (p[l].y == 0 && p[r].y == 0){ if ((p[l].x > 0) ^ (p[r].x > 0)){ return p[l].x > 0; } return p[l].x < p[r].x; } if (p[l].y == 0){ return p[l].x > 0 || p[r].y < 0; } if (p[r].y == 0){ return p[r].x < 0 && p[l].y > 0; } if ((p[l].y < 0) ^ (p[r].y < 0)){ return p[l].y > 0; } return p[l].x * p[r].y > p[l].y * p[r].x; }); rep(j, 0, N - 1) order.push_back(order[j]); rep(j, 0, N - 1) if (order[j] == (i + 1) % N){ bool ok = true; rep(k, 1, N){ if (order[j + k - 1] != (i + k) % N) ok = false; } if (ok){ cout << "1\n"; return; } } } } // No cout << "-1\n"; }