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>
using namespace std;

#define db long double
const db eps = 1e-6;
int sgn(db a, db b = 0) {
	a -= b;
	return (a > eps) - (a < -eps);
}

struct poi {
	db x, y;
	void r() { cin >> x; cin >> y; }
	void w() { cout << x << ' ' << y << '\n'; }
	poi operator -(poi p) {
		return {x - p.x, y - p.y};
	}
	poi operator +(poi p) {
		return {x + p.x, y + p.y};
	}
	poi operator *(db d) {
		return {x * d, y * d};
	}
	poi operator /(db d) {
		return {x / d, y / d};
	}
	bool operator ==(poi p) {
		return !sgn(x, p.x) && !sgn(y, p.y);
	}
	db dot(poi p) {
		return x * p.x + y * p.y;
	}
	db cross(poi p) {
		return x * p.y - y * p.x;
	}
	db len() { return sqrt(x * x + y * y); }
	db len2() { return x * x + y * y; }
	poi proj(poi p, poi q) {
		db s = (*this - p).dot(q - p) / (q - p).len2();
		return p + (q - p) * s;
	}
	db dis(poi p, poi q) {
		if((*this - p).dot(q - p) < 0) return (*this - p).len();
		if((*this - q).dot(p - q) < 0) return (*this - q).len();
		return abs((*this - p).cross(q - p) / (q - p).len());
	}
};
db xmul(poi a, poi b, poi c) {
	return (b - a).cross(c - a);
}

int ccw(poi a, poi b, poi c) {
	poi u = b - a, v = c - a;
	if(u.cross(v) > eps) return 1;
	if(u.cross(v) < -eps) return -1;
	if(u.dot(v) < -eps) return -2;
	if(u.len2() + eps < v.len2()) return 2;
	return 0;
}
bool si(poi a, poi b, poi c, poi d) {
	return ccw(a, b, c) * ccw(a, b, d) <= 0 &&
		ccw(c, d, a) * ccw(c, d, b) <= 0;
}
poi li(poi a, poi b, poi c, poi d) {
	db u = xmul(c, d, a), v = xmul(c, d, b);
	return (a * v - b * u) / (v - u);
}

const int N = 111;
poi p[N];

int main() {
	ios :: sync_with_stdio(false);
	int n; cin >> n;
	for(int i = 0; i < n; i ++)
		p[i].r();
	p[n] = p[0];
	bool conv = true;
	for(int i = 0; i < n - 1; i ++)
		if(ccw(p[i], p[i + 1], p[i + 2]) == -1)
			conv = false;
	cout << conv << '\n';

	return 0;
}