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;
double EPS = 1e-8;
const double PI = acos(-1);
int sgn(double a, double b = 0) {
  return a < b - EPS ? -1 : a > b + EPS ? 1 : 0;
}
double sqr(double a) { return sqrt(max(a, (double)0)); }
struct Point {
  double add(double a, double b) {
    if (abs(a + b) < EPS * (abs(a) + abs(b))) return 0;
    return a + b;
  }
  double x, y;
  Point() {}
  Point(double x, double y) : x(x), y(y) {}
  Point operator+(Point p) { return Point(add(x, p.x), add(y, p.y)); }
  Point operator-(Point p) { return Point(add(x, -p.x), add(y, -p.y)); }
  Point operator*(double d) { return Point(x * d, y * d); }
  Point operator/(double d) { return Point(x / d, y / d); }
  bool operator==(Point p) { return !sgn(dist(p)); }
  bool operator<(Point p) { return (p.x != x) ? p.x < x : p.y < y; }
  double norm() { return sqr(x * x + y * y); }
  double dist(Point a) { return (*this - a).norm(); }
  double dot(Point a) { return x * a.x + y * a.y; }
  double cross(Point a) { return x * a.y - y * a.x; }
  Point rotate(double r, Point p = Point(0, 0)) {
    double ta = cos(r) * (x - p.x) - sin(r) * (y - p.y) + p.x;
    double tb = sin(r) * (x - p.x) + cos(r) * (y - p.y) + p.y;
    return Point(ta, tb);
  }
  double arg() {
    if (sgn(x) > 0) return atan(y / x);
    if (sgn(x) < 0) return atan(y / x) + PI;
    if (sgn(y) > 0) return PI / 2;
    if (sgn(y) < 0) return 3 * PI / 2;
    return 0;
  }
};
int ccw(Point a, Point b, Point c) {
  b = b - a;
  c = c - a;
  if (b.cross(c) > 0) return +1;
  if (b.cross(c) < 0) return -1;
  if (b.dot(c) < 0) return +2;
  if (b.norm() < c.norm()) return -2;
  return 0;
}
struct Polygon {
  vector<Point> v;
  Polygon() {}
  Polygon(int n) { v.resize(n); }
  bool isConvex() {
    for (int i = 0; i < v.size(); i++) {
      if (ccw(v[(i + v.size() - 1) % v.size()], v[(i) % v.size()],
              v[(i + 1) % v.size()]) <= 0)
        return false;
    }
    return true;
  }
};
int main(void) {
  int n;
  cin >> n;
  Polygon p(n);
  for (int i = 0; i < n; i++) cin >> p.v[i].x >> p.v[i].y;
  cout << p.isConvex() << endl;
  return 0;
}
