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;
class Point {
 public:
  double x, y;
  Point(double x = 0, double y = 0) : x(x), y(y) {}
  Point operator+(Point p) { return Point(x + p.x, y + p.y); }
  Point operator-(Point p) { return Point(x - p.x, y - p.y); }
  Point operator*(double a) { return Point(x * a, y * a); }
  double operator*(Point p) { return dot(p); }
  Point operator/(double a) { return Point(x / a, y / a); }
  double abs() { return sqrt(norm()); }
  double norm() { return x * x + y * y; }
  bool operator<(const Point &p) const { return x != p.x ? x < p.x : y < p.y; }
  bool operator==(const Point &p) const {
    return fabs(x - p.x) < (1e-10) && fabs(y - p.y) < (1e-10);
  }
  double dot(Point p) { return x * p.x + y * p.y; }
  double cross(Point p) { return x * p.y - y * p.x; }
};
class Circle {
 public:
  Point c;
  double r;
  Circle(Point c = Point(), double r = 0.0) : c(c), r(r) {}
};
struct Segment {
  Point p1, p2;
};
typedef Segment Line;
typedef vector<Point> Polygon;
double v_norm(Point p) { return p.x * p.x + p.y * p.y; }
double abs(Point p) { return sqrt(v_norm(p)); }
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; }
bool isOrthogonal(Point a, Point b) {
  return (fabs((a * b) - (0.0)) < (1e-10));
}
bool isParallel(Point a, Point b) {
  return (fabs((cross(a, b)) - (0.0)) < (1e-10));
}
Point projection(Segment s, Point p) {
  Point base = s.p2 - s.p1;
  double r = dot((p - s.p1), base) / v_norm(base);
  return s.p1 + base * r;
}
Point reflection(Segment s, Point p) { return p + (projection(s, p) - p) * 2; }
static const int COUNTER_CLOCKWISE = 1;
static const int CLOCKWISE = -1;
static const int ONLINE_BACK = 2;
static const int ONLINE_FRONT = -2;
static const int ON_SEGMENT = 0;
int ccw(Point p0, Point p1, Point p2) {
  Point a = p1 - p0;
  Point b = p2 - p0;
  if (cross(a, b) > (1e-10)) return COUNTER_CLOCKWISE;
  if (cross(a, b) < -(1e-10)) return CLOCKWISE;
  if (dot(a, b) < -(1e-10)) return ONLINE_BACK;
  if (a.norm() < b.norm()) return ONLINE_FRONT;
  return ON_SEGMENT;
}
bool intersect(Point p1, Point p2, Point p3, Point p4) {
  return ((ccw(p1, p2, p3) * ccw(p1, p2, p4) <= 0) &&
          (ccw(p3, p4, p1) * ccw(p3, p4, p2) <= 0));
}
bool intersect(Segment s1, Segment s2) {
  return intersect(s1.p1, s1.p2, s2.p1, s2.p2);
}
double getDistance(Point a, Point b) { return abs(a - b); }
double getDistanceLP(Line l, Point p) {
  return abs(cross(l.p2 - l.p1, p - l.p1) / abs(l.p2 - l.p1));
}
double getDistanceSP(Segment s, Point p) {
  {};
  {};
  if (dot(s.p2 - s.p1, p - s.p1) < 0.0) return abs(p - s.p1);
  if (dot(s.p1 - s.p2, p - s.p2) < 0.0) return abs(p - s.p2);
  return getDistanceLP(s, p);
}
double getDistance(Segment s1, Segment s2) {
  if (intersect(s1, s2)) return 0.0;
  {};
  {};
  return min(min(getDistanceSP(s1, s2.p1), getDistanceSP(s1, s2.p2)),
             min(getDistanceSP(s2, s1.p1), getDistanceSP(s2, s1.p2)));
}
Point getCrossPoint(Segment s1, Segment s2) {
  Point base = s2.p2 - s2.p1;
  double d1 = abs(cross(base, s1.p1 - s2.p1));
  double d2 = abs(cross(base, s1.p2 - s2.p1));
  double t = d1 / (d1 + d2);
  return s1.p1 + (s1.p2 - s1.p1) * t;
}
pair<Point, Point> getCrossPoints(Circle c, Line l) {
  Point pr = projection(l, c.c);
  Point e = (l.p2 - l.p1) / abs(l.p2 - l.p1);
  double base = sqrt(c.r * c.r - (pr - c.c).norm());
  return make_pair(pr + e * base, pr - e * base);
}
static const int IN_POLYGON = 2;
static const int OUT_POLYGON = 1;
static const int ON_POLYGON = 0;
int contains(Polygon g, Point p) {
  int n = g.size();
  bool x = false;
  for (int i = (0); i < (int)(n); i++) {
    Point a = g[i] - p, b = g[(i + 1) % n] - p;
    if (abs(cross(a, b)) < (1e-10) && dot(a, b) < (1e-10)) return OUT_POLYGON;
    if (a.y > b.y) swap(a, b);
    if (a.y < (1e-10) && (1e-10) < b.y && cross(a, b)) x = !x;
  }
  return (x ? IN_POLYGON : ON_POLYGON);
}
Polygon ConvexHull(Polygon s, bool containsPointOnline = false) {
  Polygon u, l;
  if (s.size() < 3) return s;
  sort(s.begin(), s.end());
  u.push_back(s[0]);
  u.push_back(s[1]);
  l.push_back(s[s.size() - 1]);
  l.push_back(s[s.size() - 2]);
  auto conditionContaining = [](int ccw, bool containsPointOnline) -> bool {
    if (containsPointOnline)
      return ccw == COUNTER_CLOCKWISE;
    else
      return ccw != CLOCKWISE;
  };
  for (int i = 2; i < s.size(); i++) {
    for (int n = u.size();
         (n >= 2) && conditionContaining(ccw(u[n - 2], u[n - 1], s[i]),
                                         containsPointOnline);
         n--) {
      u.pop_back();
    }
    u.push_back(s[i]);
  }
  for (int i = s.size() - 3; i >= 0; i--) {
    for (int n = l.size();
         n >= 2 && conditionContaining(ccw(l[n - 2], l[n - 1], s[i]),
                                       containsPointOnline);
         n--)
      l.pop_back();
    l.push_back(s[i]);
  }
  reverse(l.begin(), l.end());
  for (int i = u.size() - 2; i >= 1; i--) l.push_back(u[i]);
  double tmpMax = l[0].y;
  int rotIndex = 0;
  for (int i = (1); i < (int)(l.size()); i++) {
    if (l[i].y < tmpMax) {
      rotIndex = i;
      tmpMax = l[i].y;
    }
  }
  rotate(l.begin(), l.begin() + rotIndex, l.end());
  return l;
}
bool isConvex(Polygon poly) {
  bool ok = true;
  for (int i = (0); i < (int)(poly.size() - 1); i++) {
    int k = poly.size();
    if (cross(poly[i % k] - poly[(i + 1) % k],
              poly[(i + 1) % k] - poly[(i + 2) % k]) <= 0) {
      ok = false;
      break;
    }
  }
  return ok;
}
int main() {
  int n;
  cin >> n;
  Polygon poly;
  for (int i = (0); i < (int)(n); i++) {
    Point p;
    cin >> p.x >> p.y;
    poly.push_back(p);
  }
  cout << (isConvex(poly) ? "1" : "0") << endl;
END:
  return 0;
}
