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;
typedef long long ll;
typedef pair<ll, ll> lpair;
const ll MOD = 1e9 + 7;
const ll INF = 1e18;
#define rep(i,m,n) for(ll i = (m); i < (n); i++)
#define rrep(i,m,n) for(ll i = (m); i >= (n); i--)
#define print(x) cout << (x) << endl;
#define print2(x,y) cout << (x) << " " << (y) << endl;
#define printa(x,n) for(ll i = 0; i < n; i++){ cout << (x[i]) << " ";} cout<<endl;

#define EPS (1e-10)
#define EQ(a,b) (abs((a) - (b)) < EPS)
typedef complex<double> P;
double dot(P a, P b){ //内積
    return (a.real() * b.real() + a.imag() * b.imag());
}

double cross(P a, P b){ //外積
    return (a.real() * b.imag() - a.imag() * b.real());
}

bool is_orth(P a1, P a2, P b1, P b2){ //垂直か
    return EQ(dot(a1 - a2, b1 - b2), 0.0);
}

bool is_para(P a1, P a2, P b1, P b2){ //平行か
    return EQ(cross(a1 - a2, b1 - b2), 0.0);
}

bool is_online(P a, P b, P c){ //cが線分上か
    return (abs(a-c) + abs(c-b) < abs(a-b) + EPS);
}

bool distance_lp(P a, P b, P c){ //直線abと点cの距離
    return abs(cross(b-a, c-a)) / abs(b-a);
}

double norm(P a){
  return a.real() * a.real() +a.imag() *a.imag();
}

ll ccw(P p0,P p1,P p2){
  P a = p1-p0;
  P b = p2-p0;
  if(cross(a,b) > EPS) return 1;
  if(cross(a,b) < -EPS) return -1;
  if(dot(a,b) < -EPS) return 2;
  if(abs(a) < abs(b)) return -2;
  return 0;
}

bool is_intersect(P p1, P p2, P p3, P p4){
  return (ccw(p1,p2,p3) * ccw(p1,p2,p4) <= 0 &&
      ccw(p3,p4,p1) * ccw(p3,p4,p2) <= 0 );
}

P intersect_pos(P a1, P a2, P b1, P b2){ //直線同士の交点
    P a = a2 - a1;
    P b = b2 - b1;
    return a1 + a * cross(b, b1 - a1) / cross(b, a);
}

double getDistanceLP(P a1, P a2, P b){
    return abs(cross(a2-a1, b-a1) / abs(a2 - a1));
}

double getDistanceSP(P a1, P a2, P b){
    if(dot(a2 - a1, b - a1) < EPS) return abs(b - a1);
    if(dot(a1 - a2, b - a2) < EPS) return abs(b - a2);
    return getDistanceLP(a1, a2, b);
}
double getDistance(P a1, P a2, P b1, P b2){
    if(is_intersect(a1, a2, b1, b2)) return 0.0;
    double v1 = min(getDistanceSP(a1, a2, b1), getDistanceSP(a1, a2, b2));
    double v2 = min(getDistanceSP(b1, b2, a1), getDistanceSP(b1, b2, a2));
    return min(v1,v2);
}

#define printP(P) cout << "(" << P.real() << ", " << P.imag() << ")" << endl;




int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll N;
    cin >> N;
    double x[110], y[110];
    vector<P> p;
    rep(i,0,N){
        cin >> x[i] >> y[i];
        P t(x[i], y[i]);
        p.push_back(t);
    }
    rep(i,0,N){
        double sin = cross(p[(i-1+N)%N] - p[i], p[(i+1)%N] - p[i]) * -1;
        if(sin < 0){
            print(0);
            return 0;
        }
    }
    print(1);


}
