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 rep(i,n) for(int (i)=0;(i)<(n);(i)++)
using namespace std;

typedef bool B;
typedef long double D;
typedef complex<D> P;
typedef vector<P> VP;
typedef struct {P s,t;} L;
typedef vector<L> VL;
typedef struct {P c;D r;} C;
typedef vector <C> VC;

const D eps=1.0e-10;
const D pi=acos(-1.0);
template<class T> bool operator==(T a, T b){return abs(a-b)< eps;}
template<class T> bool operator< (T a, T b){return a < b-eps;}
template<class T> bool operator<=(T a, T b){return a < b+eps;}
template<class T> int sig(T r) {return (r==0||r==-0) ? 0 : r > 0 ? 1 : -1;}
#define X real()
#define Y imag()

D ip(P a, P b) {return a.X * b.X + a.Y * b.Y;}
D ep(P a, P b) {return a.X * b.Y - a.Y * b.X;}
D sq(D a) {return sqrt(max(a, (D)0));}
P vec(L l){return l.t-l.s;}
inline P input(){D x,y;cin >> x >> y; return P(x,y);}
// ???????????¬????????¨???

// ???????????? verify AOJ CGL_1_C
enum CCW{
	LEFT = 1,
	RIGHT = 2,
	BACK = 4,
	FRONT = 8,
	MID = 16,
	ON=FRONT|BACK|MID
};

inline int ccw(P base, P a, P b) {              //???a??¨???b???????????????????????????
	a -= base; b -= base;
	if (ep(a, b) > 0)
		return LEFT;    // counter clockwise
	if (ep(a, b) < 0)
		return RIGHT;   // clockwise
	if (ip(a, b) < 0)
		return BACK;    // b--base--a on line
	if (norm(a) < norm(b))
		return FRONT;   // base--a--b on line
	// otherwise
	return MID;      // base--b--a on line  a??¨b????????????????????????
}



// ??????????????????
inline B cmp_x(const P &a,const P &b){
	return (abs(a.X-b.X)<eps ) ?  a.Y<b.Y : a.X<b.X;
}  // base x
inline B cmp_y(const P &a,const P &b){
	return (abs(a.Y-b.Y)<eps ) ?  a.X<b.X : a.Y<b.Y;
}  // base y
inline B cmp_a(const P &a,const P &b){
	return (abs(arg(a)-arg(b))<eps ) ?  norm(a) < norm(b) : arg(a)<arg(b);
} // base arg

// ????§???¢

// Area
// Verify AOJ 1100
D area(VP pol){
	int n=pol.size();
	D sum=0.0;
	rep(i,n){
		D x=pol[i%n].X-pol[(i+1)%n].X;
		D y=pol[i%n].Y+pol[(i+1)%n].Y;
		sum+=x*y;
	}
	return abs(sum/2.0);
}

B is_convex(VP pol){
	int n=pol.size(),k=0;
	rep(i,n) if(ccw(pol[i%n],pol[(i+1)%n])==RIGHT) return false;
	return true;
}


// Convex_hull
// Verify AOJ 0063

VP convex_hull(VP pol){
	int n=pol.size(),k=0;
	sort(pol.begin(),pol.end(),cmp_x);
	VP res(2*n);

	// down
	rep(i,n){
		//????§???¢????????????????????????????????´??????<0????????´???????????¨
		while( k>1 && ep(res[k-1]-res[k-2],pol[i]-res[k-1])<0) k--;
		res[k++]=pol[i];
	}
	// up
	for(int i=n-2,t=k;i>=0;i--){
		//????§???¢????????????????????????????????´??????<0????????´???????????¨
		while( k>t && ep(res[k-1]-res[k-2],pol[i]-res[k-1])<0) k--;
		res[k++]=pol[i];
	}
	res.resize(k-1);
	return res;
}


// ????§???¢??????????????????(???????§???¢??????)
//verify AOJ CGL_3-C
int in_polygon(VP pol,P p){
	int n=pol.size();
	int res=0;
	rep(i,n){
		if(ccw(pol[i],pol[(i+1)%n],p)==MID)
			return 1;
		D vt=(p.Y-pol[i].Y)/(pol[(i+1)%n].Y-pol[i].Y);
		D dx=pol[(i+1)%n].X-pol[i].X;
		if((pol[i].Y<=p.Y)&&(p.Y< pol[(i+1)%n].Y)&&(p.X<pol[i].X+vt*dx))res++;
		if((pol[i].Y> p.Y)&&(p.Y>=pol[(i+1)%n].Y)&&(p.X<pol[i].X+vt*dx))res--;
	}
	return res?2:0;
}

int main(void){
	int n;
	cin >> n;
	VP pol;
	rep(i,n) pol.push_back(input());
	cout << is_convex(pol) << endl;
	return 0;
}