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;
constexpr double eps = 1e-10;
constexpr long mod = 1000000007;
constexpr short shINF = 32767;
constexpr long loINF = 2147483647;
constexpr long long llINF = 9223372036854775807;
struct Order {
  bool operator()(pair<long long, long long> const &a,
                  pair<long long, long long> const &b) const {
    return a.first > b.first || ((a.first == b.first) && (a.second > b.second));
  }
};
typedef struct _PT {
  long double x, y;
  _PT() {}
  _PT(long double x, long double y) : x(x), y(y) {}
  _PT operator+(_PT p) { return _PT(x + p.x, y + p.y); }
  _PT operator-(_PT p) { return _PT(x - p.x, y - p.y); }
  _PT operator*(long double d) { return _PT(d * x, d * y); }
  bool operator<(const struct _PT &e) const {
    return x == e.x ? (y < e.y) : x < e.x;
  }
  bool operator>(const struct _PT &e) const {
    return x == e.x ? (y > e.y) : x > e.x;
  }
  long double dist(_PT p) {
    return sqrt((x - p.x) * (x - p.x) + (y - p.y) * (y - p.y));
  }
  long double dot(_PT v) { return x * v.x + y * v.y; }
  long double det(_PT v) { return x * v.y - v.x * y; }
  long double norm(void) { return sqrt(x * x + y * y); }
  long double twiceNorm(void) { return x * x + y * y; }
  bool is_parallel(_PT v) { return (abs(x * v.y - v.x * y) < eps); }
} P;
class Plane {
 private:
  static bool cmp_x(const P &p1, const P &p2) {
    if (p1.x != p2.x) return p1.x < p2.x;
    return p1.y < p2.y;
  }

 public:
  P intersection(P p1, P p2, P q1, P q2) {
    return p1 + (p2 - p1) * ((q2 - q1).det(q1 - p1) / (q2 - q1).det(p2 - p1));
  }
  bool on_seq(P p1, P p2, P q) {
    return (abs((p1 - q).det(p2 - q)) < eps) && ((p1 - q).dot(p2 - q) < (eps));
  }
  bool have_intersection(P p1, P p2, P q1, P q2) {
    if (abs((p1 - p2).det(q1 - q2)) > eps) {
      P r = intersection(p1, p2, q1, q2);
      return (on_seq(p1, p2, r) && on_seq(q1, q2, r));
    } else
      return (on_seq(p1, p2, q1) || on_seq(p1, p2, q2) || on_seq(q1, q2, p1) ||
              on_seq(q1, q2, p2));
  }
  P projection(P v1, P v2) { return (v1) * ((v1).dot(v2) / v1.twiceNorm()); }
  long double disPointToLine(P p1, P p2, P q) {
    return (p1 + (projection((p2 - p1), (q - p1)))).dist(q);
  }
  long double disPointToLineSeg(P p1, P p2, P q) {
    if ((p1 - p2).dot(q - p2) < eps) return q.dist(p2);
    if ((p2 - p1).dot(q - p1) < eps)
      return q.dist(p1);
    else
      return (p1 + projection(p2 - p1, q - p1)).dist(q);
  }
  long double disLineSeg(P p1, P p2, P q1, P q2) {
    if (have_intersection(p1, p2, q1, q2))
      return 0.0;
    else
      return min({disPointToLineSeg(p1, p2, q1), disPointToLineSeg(p1, p2, q2),
                  disPointToLineSeg(q1, q2, p1),
                  disPointToLineSeg(q1, q2, p2)});
  }
  vector<P> convexHull(vector<P> &point) {
    long long n = point.size();
    vector<P> qs(n * 2);
    sort(point.begin(), point.end(), cmp_x);
    long k = 0;
    for (long long i = 0; i < (n); i++) {
      while (k > 1 && (qs[k - 1] - qs[k - 2]).det(point[i] - qs[k - 1]) <= 0)
        k--;
      qs[k++] = point[i];
    }
    for (long i = n - 2, t = k; i >= 0; i--) {
      while (k > t && (qs[k - 1] - qs[k - 2]).det(point[i] - qs[k - 1]) <= 0)
        k--;
      qs[k++] = point[i];
    }
    qs.resize(k - 1);
    return qs;
  }
  long double getArea(vector<P> &point) {
    long double s = 0;
    long long n = point.size();
    for (long long i = 0; i < (n - 1); i++) s += point[i].det(point[i + 1]);
    s += point[n - 1].det(point[0]);
    return abs(s) * 0.5;
  }
  long double getAngle(P v1, P v2) {
    return acos(v1.dot(v2) / sqrt(v1.twiceNorm() * v2.twiceNorm()));
  }
};
int main(void) {
  Plane pl;
  int N;
  cin >> N;
  vector<P> point(N);
  for (long long i = 0; i < (N); i++) cin >> point[i].x >> point[i].y;
  int ret = (pl.convexHull(point)).size();
  if (N == ret)
    cout << 1 << endl;
  else
    cout << 0 << endl;
}
