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 <algorithm>
#include <vector>
#include <string>
#include <utility>
#include <cmath>
#include <cstdio>
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define F first
#define S second
using namespace std;
template<class T>bool chmax(T &a, const T &b) { if(a < b){ a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if(a > b){ a = b; return 1; } return 0; }
using ll = long long;
using pi = pair<int,int>;
const double EPS = 1e-10;
struct Vec2 {
  double x;
  double y;

  Vec2() : x(0.0),y(0.0){} 
  Vec2(double _x,double _y) :x(_x),y(_y){}  
  
  Vec2 operator+(const Vec2& other) const { return { x + other.x , y + other.y }; }
  Vec2 operator-(const Vec2& other) const { return { x - other.x , y - other.y }; }
  bool operator==(const Vec2& other) const { return (abs(x - other.x) < EPS && abs(y - other.y) < EPS ); }
  
  double dot(const Vec2& other) const { return x * other.x + y * other.y; }
  double cross(const Vec2& other) const { return x * other.y - y * other.x; }
  double length() const { return sqrt(x * x + y * y); }
};
// A とB のなす角θ cosθ, sinθ を返す
double Cos(const Vec2 A, const Vec2 B) { return A.dot(B) / (A.length()*B.length()); }
double Sin(const Vec2 A, const Vec2 B) { return A.cross(B) / (A.length()*B.length()); }

int main()
{
  int n; cin >> n;
  vector<Vec2> v(n);
  rep(i,n) {
    cin >> v[i].x >> v[i].y;
  }

  bool f = true;
  rep(i,n) {
    if(Sin(v[(i+1)%n] - v[i], v[(i+2)%n] - v[i]) < 0) f = false;
  }
  if(f) cout << 1 << "\n";
  else cout << 0 << "\n";
  return 0;
}

