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 double EPS = 1e-8;
const double INF = 1e12;
namespace std {
bool operator<(const complex<double>& a, const complex<double>& b) {
  return real(a) != real(b) ? real(a) < real(b) : imag(a) < imag(b);
}
}  // namespace std
double cross(const complex<double>& a, const complex<double>& b) {
  return imag(conj(a) * b);
}
double dot(const complex<double>& a, const complex<double>& b) {
  return real(conj(a) * b);
}
struct L : public vector<complex<double> > {
  L(const complex<double>& a, const complex<double>& b) {
    push_back(a);
    push_back(b);
  }
};
struct C {
  complex<double> p;
  double r;
  C(const complex<double>& p, double r) : p(p), r(r) {}
};
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;
}
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 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 intersectLP(const L& l, const complex<double>& p) {
  return abs(cross(l[1] - p, l[0] - p)) < EPS;
}
bool intersectSP(const L& s, const complex<double>& p) {
  return abs(s[0] - p) + abs(s[1] - p) - abs(s[1] - s[0]) < EPS;
}
bool orthogonalLL(const L& l1, const L& l2) {
  return (dot(l1[0] - l1[1], l2[0] - l2[1]) <= EPS &&
          dot(l1[0] - l1[1], l2[0] - l2[1]) >= -EPS);
}
bool parallelLL(const L& l1, const L& l2) {
  return (cross(l1[0] - l1[1], l2[0] - l2[1]) <= EPS &&
          cross(l1[0] - l1[1], l2[0] - l2[1]) >= -EPS);
}
complex<double> projection(const L& l, const complex<double>& p) {
  double t = dot(p - l[0], l[0] - l[1]) / norm(l[0] - l[1]);
  return l[0] + t * (l[0] - l[1]);
}
complex<double> reflection(const L& l, const complex<double>& p) {
  return p + 2. * (projection(l, p) - p);
}
double distancePP(const complex<double>& a, const complex<double>& b) {
  return abs(a - b);
}
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 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 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])));
}
complex<double> crosspointLL(const L& l, const L& m) {
  double A = cross(l[1] - l[0], m[1] - m[0]);
  double B = cross(l[1] - l[0], l[1] - m[0]);
  if (abs(A) < EPS && abs(B) < EPS) return m[0];
  if (abs(A) < EPS) assert(false);
  return m[0] + B / A * (m[1] - m[0]);
}
double area(const vector<complex<double> >& g) {
  double A = 0.0;
  for (int i = 0; i < g.size(); i++) A += cross(g[i], g[(i + 1) % g.size()]);
  return A / 2.0;
}
vector<complex<double> > convex_full(vector<complex<double> >& ps) {
  int n = ps.size(), k = 0;
  sort(ps.begin(), ps.end());
  vector<complex<double> > ch(2 * n);
  for (int i = 0; i < n; ch[k++] = ps[i++])
    while (k >= 2 && ccw(ch[k - 2], ch[k - 1], ps[i]) == -1) --k;
  for (int i = n - 2, t = k + 1; i >= 0; ch[k++] = ps[i--])
    while (k >= t && ccw(ch[k - 2], ch[k - 1], ps[i]) == -1) --k;
  ch.resize(k - 1);
  return ch;
}
bool is_convex(vector<complex<double> >& g) {
  vector<complex<double> > cf = convex_full(g);
  if (cf.size() == g.size()) return true;
  return false;
}
int main(void) {
  int n;
  cin >> n;
  vector<complex<double> > g(n);
  for (int i = 0; i < n; i++) {
    int x, y;
    cin >> x >> y;
    g[i] = complex<double>(x, y);
  }
  if (is_convex(g))
    cout << 1 << endl;
  else
    cout << 0 << endl;
  return 0;
}
