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>
const double PI = acos(-1);
const double EPS = 1e-10;
using namespace std;
struct L : public vector<complex<double> > {
  L(const complex<double> &a, const complex<double> &b) {
    push_back(a);
    push_back(b);
  }
};
complex<double> pin() {
  double x, y;
  cin >> x >> y;
  complex<double> p(x, y);
  return p;
}
void PIN(complex<double> *a, int n) {
  for (int i = 0; i < n; i++) a[i] = pin();
}
double dot(complex<double> a, complex<double> b) { return real(conj(a) * b); }
double cross(complex<double> a, complex<double> b) { return imag(conj(a) * b); }
int ccw(complex<double> a, complex<double> b, complex<double> c) {
  b -= a;
  c -= a;
  if (cross(b, c) > 0) return +1;
  if (cross(b, c) < 0) return -1;
  if (dot(b, c) < 0) return +2;
  if (norm(b) < norm(c)) return -2;
  return 0;
}
complex<double> projection(L a, complex<double> p) {
  double t = dot(p - a[0], a[0] - a[1]) / norm(a[0] - a[1]);
  return a[0] + t * (a[0] - a[1]);
}
complex<double> reflection(L a, complex<double> p) {
  return p + 2.0 * (projection(a, p) - p);
}
bool intersectLL(const L &l, const L &m) {
  return abs(cross(l[1] - l[0], m[1] - m[0])) > EPS ||
         abs(cross(l[1] - l[0], m[0] - l[0])) < EPS;
}
bool intersectLS(const L &l, const L &s) {
  return cross(l[1] - l[0], s[0] - l[0]) * cross(l[1] - l[0], s[1] - l[0]) <
         EPS;
}
bool intersectLP(const L &l, const complex<double> &p) {
  return abs(cross(l[1] - p, l[0] - p)) < EPS;
}
bool intersectSS(const L &s, const L &t) {
  return ccw(s[0], s[1], t[0]) * ccw(s[0], s[1], t[1]) <= 0 &&
         ccw(t[0], t[1], s[0]) * ccw(t[0], t[1], s[1]) <= 0;
}
bool intersectSP(const L &s, const complex<double> &p) {
  return abs(s[0] - p) + abs(s[1] - p) - abs(s[1] - s[0]) < EPS;
}
complex<double> intersect_ls(L a, L b) {
  double t1 = abs(cross(a[1] - a[0], b[0] - a[0]));
  double t2 = abs(cross(a[1] - a[0], b[1] - a[0]));
  return b[0] + (b[1] - b[0]) * t1 / (t1 + t2);
}
double distanceLP(const L &l, const complex<double> &p) {
  return abs(p - projection(l, p));
}
double distanceLL(const L &l, const L &m) {
  return intersectLL(l, m) ? 0 : distanceLP(l, m[0]);
}
double distanceLS(const L &l, const L &s) {
  if (intersectLS(l, s)) return 0;
  return min(distanceLP(l, s[0]), distanceLP(l, s[1]));
}
double distanceSP(const L &s, const complex<double> &p) {
  const complex<double> r = projection(s, p);
  if (intersectSP(s, r)) return abs(r - p);
  return min(abs(s[0] - p), abs(s[1] - p));
}
double distanceSS(const L &s, const L &t) {
  if (intersectSS(s, t)) return 0;
  return min(min(distanceSP(s, t[0]), distanceSP(s, t[1])),
             min(distanceSP(t, s[0]), distanceSP(t, s[1])));
}
double area(const vector<complex<double> > &g) {
  double S = 0;
  for (int i = 0; i < g.size(); i++) {
    S += (cross(g[i], g[(i + 1) % g.size()]));
  }
  return abs(S / 2.0);
}
bool inconvex(const vector<complex<double> > &g) {
  int n = g.size();
  for (int i = 0; i < n; i++)
    if (ccw(g[(i + n - 1) % n], g[i % n], g[(i + 1) % n]) != 1) return false;
  return true;
}
int main() {
  int n;
  cin >> n;
  vector<complex<double> > g(n);
  PIN(&g[0], n);
  cout << inconvex(g) << endl;
}
