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;
const int INF = 1e9;
const int MOD = 1e9 + 7;
const double EPS = 1e-6;
template <typename T1, typename T2>
ostream& operator<<(ostream& os, const pair<T1, T2>& p) {
  return os << '(' << p.first << ',' << p.second << ')';
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& a) {
  os << '[';
  for (int i = int(0); i < int(a.size()); i++) os << (i ? " " : "") << a[i];
  return os << ']';
}
int Signum(double x) { return x < -EPS ? -1 : x > EPS ? 1 : 0; }
struct Point {
  double x, y;
  Point() {}
  Point(double x, double y) : x(x), y(y) {}
  Point& operator+=(Point p) {
    x += p.x, y += p.y;
    return *this;
  }
  Point& operator-=(Point p) {
    x -= p.x, y -= p.y;
    return *this;
  }
  Point& operator*=(double c) {
    x *= c, y *= c;
    return *this;
  }
  Point& operator/=(double c) {
    x /= c, y /= c;
    return *this;
  }
};
Point operator+(Point a, Point b) { return a += b; }
Point operator-(Point a, Point b) { return a -= b; }
Point operator*(Point a, double c) { return a *= c; }
Point operator*(double c, Point a) { return a *= c; }
Point operator/(Point a, double c) { return a /= c; }
bool operator==(Point a, Point b) {
  return abs(a.x - b.x) < EPS && abs(a.y - b.y) < EPS;
}
bool operator!=(Point a, Point b) { return !(a == b); }
double Abs(Point p) { return sqrt(p.x * p.x + p.y * p.y); }
double Abs2(Point p) { return p.x * p.x + p.y * p.y; }
double Arg(Point p) { return atan2(p.y, p.x); }
double Dot(Point a, Point b) { return a.x * b.x + a.y * b.y; }
double Cross(Point a, Point b) { return a.x * b.y - a.y * b.x; }
Point Rot(Point p, double t) {
  return Point(cos(t) * p.x - sin(t) * p.y, sin(t) * p.x + cos(t) * p.y);
}
int CCW(Point a, Point b, Point c) {
  b -= a, c -= a;
  if (int sign = Signum(Cross(b, c))) return sign;
  if (Dot(b, c) < -EPS) return -2;
  if (Abs2(b) < Abs2(c) - EPS) return 2;
  return 0;
}
bool IsConvex(const vector<Point>& ps) {
  int n = ps.size(), res = true;
  for (int i = int(0); i < int(n); i++)
    res &= CCW(ps[i], ps[(i + 1) % n], ps[(i + 2) % n]) >= 1;
  return res;
}
int main() {
  for (int n; cin >> n && n;) {
    vector<Point> ps(n);
    for (auto& p : ps) cin >> p.x >> p.y;
    cout << IsConvex(ps) << endl;
  }
}
