For a given polygon g, print "1" if g is a convex polygon, "0" otherwise. Here, in a convex polygon, all interior angles are less than or equal to 180 degrees.

g is represented by a sequence of points p1, p2,..., pn where line segments connecting pi and pi+1 (1 ≤ i ≤ n-1) are sides of the polygon. The line segment connecting pn and p1 is also a side of the polygon.

Constraints

* 3 ≤ n ≤ 100
* -10000 ≤ xi, yi ≤ 10000
* No point of the polygon will occur more than once.
* Two sides of the polygon can intersect only at a common endpoint.

Input

g is given by coordinates of the points p1,..., pn in the following format:


n
x1 y1
x2 y2
:
xn yn


The first integer n is the number of points. The coordinate of a point pi is given by two integers xi and yi. The coordinates of points are given in the order of counter-clockwise visit of them.

Output

Print "1" or "0" in a line.

Examples

Input

4
0 0
3 1
2 3
0 3


Output

1


Input

5
0 0
2 0
1 1
2 2
0 2


Output

0
#include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-9;
const ll mod=1e9+7;
const int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};

typedef complex<double> C;
typedef pair<C,C> pp;
typedef vector<C> VP;
typedef vector<pp> VPP;
#define eq(a,b) (fabs(a-b)<eps)
#define veq(a,b) (eq(a.real(),b.real())&&eq(a.imag(),b.imag()))
const C O{0,0};

void In(C& p){
	double x,y;
	cin>>x>>y;
	p=C(x,y);
}

void Out(C p){
	cout<<(int)p.real()<<' '<<(int)p.imag()<<endl;
}

double Dot(C p,C q){
	return p.real()*q.real()+p.imag()*q.imag();
}

double Det(C p,C q){
	return p.real()*q.imag()-q.real()*p.imag();
}

bool is_Convex(VP p){
	p.push_back(p[0]);
	p.push_back(p[1]);
	int n=p.size();
	for(int i=1;i<n-1;i++) if(Det(p[i]-p[i-1],p[i+1]-p[i-1])<0) return 0;
	return 1;
}

int n;
VP a;

int main(){
	cin>>n;
	a=VP(n);
	for(auto &i:a) In(i);
	cout<<is_Convex(a)<<endl;
}
