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 <iostream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <algorithm>

using namespace std;

template<class T>
struct Vec2
{
	Vec2(){}
	Vec2(T _x, T _y) : x(_x), y(_y) {}

	Vec2 operator+(const Vec2& rhs) const { return Vec2(x + rhs.x, y + rhs.y); }
	Vec2 operator-(const Vec2& rhs) const { return Vec2(x - rhs.x, y - rhs.y); }
	Vec2 operator*(T s) const { return Vec2(x*s, y*s); }
	Vec2 operator/(T s) const { return Vec2(x/s, y/s); }
	T dot(const Vec2& rhs) const { return x*rhs.x + y*rhs.y; }
	T cross(const Vec2& rhs) const { return x*rhs.y - y*rhs.x; }
	T sqlength() const { return x*x + y*y; }
	double length() const { return sqrt(sqlength()); }
	bool operator<(const Vec2& rhs) const
	{
		if (x != rhs.x) return x < rhs.x;
		return y < rhs.y;
	}

	T x;
	T y;
};

template<class T>
T cross(const Vec2<T> &O, const Vec2<T> &A, const Vec2<T> &B)
{
	return (A - O).cross(B - O);
}

template<class T>
bool IsConvex(const vector<Vec2<T> >& poly)
{
	for (size_t i = 0; i < poly.size() - 2; i++) {
		if (cross(poly[i + 1], poly[i + 2],  poly[i]) < 0 ) {
			return false;
		}
	}
	return true;
}

int main()
{
	typedef Vec2<long long> Vec;

	int n;
	cin >> n;
	vector<Vec> poly(n);
	for (int i = 0; i < n; i++) {
		int x, y;
		cin >> x >> y;
		poly[i] = Vec(x, y);
	}
	poly.push_back(poly[0]);
	poly.push_back(poly[1]);
	cout << IsConvex(poly) << endl;
	return 0;
}
