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;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
template <typename T>
void O(T t) {
  cout << t << endl;
}
const double EPS = 1e-8;
const double INF = 1e12;
typedef complex<double> P;
namespace std {
bool operator<(const P &a, const P &b) {
  return real(a) != real(b) ? real(a) < real(b) : imag(a) < imag(b);
}
bool sorty(const P &a, const P &b) {
  return imag(a) != imag(b) ? imag(a) < imag(b) : real(a) < real(b);
}
}  // namespace std
double cross(const P &a, const P &b) { return imag(conj(a) * b); }
double dot(const P &a, const P &b) { return real(conj(a) * b); }
struct L : public vector<P> {
  L(){};
  L(const P &a, const P &b) {
    push_back(a);
    push_back(b);
  }
};
struct C {
  P p;
  double r;
  C(){};
  C(const P &p, double r) : p(p), r(r) {}
};
int ccw(P a, P b, P 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;
}
int linejudge(const L &ab, const L &cd) {
  P a = ab[1] - ab[0], b = cd[1] - cd[0];
  if (abs(cross(a, b)) < EPS) {
    return 2;
  } else if (abs(dot(a, b)) < EPS) {
    return 1;
  }
  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 intersectLP(const L &l, const P &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 P &p) {
  return abs(s[0] - p) + abs(s[1] - p) - abs(s[1] - s[0]) < EPS;
}
P projection(const L &l, const P &p) {
  double t = dot(p - l[0], l[0] - l[1]) / norm(l[0] - l[1]);
  return l[0] + t * (l[0] - l[1]);
}
P reflection(const L &l, const P &p) {
  return p + 2.0 * (projection(l, p) - p);
}
double distanceLP(const L &l, const P &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 P &p) {
  const P 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 distancePP(const P &p, const P &q) { return abs(p - q); }
P crosspoint(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]);
}
P verticalvector(const P &a, const P &b) {
  if (a.real() == b.real()) {
    return {1.0, 0};
  }
  if (a.imag() == b.imag()) {
    return {0, 1.0};
  }
  P p = a - b;
  P res = {-p.imag(), p.real()};
  return res / abs(p);
}
pair<P, P> crosspointCircle(const C &a, const C &b) {
  P m = (a.p + b.p) / 2.0;
  P vv = verticalvector(a.p, b.p);
  double u = sqrt(a.r * a.r - norm(a.p - b.p) / 4.0);
  P A = m + u * vv, B = m - u * vv;
  return make_pair(A, B);
}
double calc_triangle(P a, P b, P c) {
  P ba = (b - a);
  P ca = (c - a);
  return (real(ba) * imag(ca) - imag(ba) * real(ca)) / 2.0;
}
double calc_area(const vector<P> &g) {
  double res = 0;
  for (int i = 0; i < (int)(g.size() - 2); ++i) {
    res += calc_triangle(g[0], g[(i + 1) % g.size()], g[(i + 2) % g.size()]);
  }
  return res;
}
bool is_convex(const vector<P> &g) {
  for (int i = 0; i < (int)(g.size() - 2); ++i) {
    if (calc_triangle(g[0], g[(i + 1) % g.size()], g[(i + 2) % g.size()]) <=
        EPS) {
      return false;
    }
  }
  return true;
}
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n;
  double x, y;
  cin >> n;
  vector<P> g;
  for (int i = 0; i < (int)(n); ++i) {
    cin >> x >> y;
    g.push_back({x, y});
  }
  cout << is_convex(g) << endl;
  return 0;
}
