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 <iostream>
#include <cmath>
#include <vector>
using namespace std;

inline double add(double a, double b){
    return abs(a+b)<(1e-10)*(abs(a)+abs(b)) ? 0.0 : a+b;
}

struct vec{
    double x,y;
    vec operator-(vec b){
        return (vec){add(x,-b.x),add(y,-b.y)};
    }
    vec operator+(vec b){
        return (vec){add(x,b.x),add(y,b.y)};
    }
    vec operator*(double d){
        return (vec){x*d,y*d};
    }
    double dot(vec v){
        return add(x*v.x,y*v.y);
    }
    double cross(vec v){
        return add(x*v.y,-y*v.x);
    }
    double norm(){
        return sqrt(x*x+y*y);
    }
};
typedef vector<vec> polygon;

int ccw(vec& a, vec& b, vec& c){
    vec ab = b-a, ac = c-a;
    double o = ab.cross(ac);
    if(o>0) return 1; //CCW
    if(o<0) return -1; //CW
    if(ab.dot(ac)<0){
        return 2; //C-A-B
    }else{
        if(ab.dot(ab)<ac.dot(ac)){
            return -2; //A-B-C
        }else{
            return 0; //A-C-B
        }
    }
}

bool isConvex(polygon& g){
    int n=g.size()-2;
    for(int i=0;i<n;i++){
        if(!~ccw(g[i],g[i+1],g[i+2]))return false;
    }
    return true;
}

int main(){
    int n;
    cin >> n;
    polygon g;
    vec v;
    while(n--){
        cin >> v.x >> v.y;
        g.push_back(v);
    }
    g.push_back(g[0]);
    g.push_back(g[1]);
    cout.precision(1);
    cout << fixed;
    cout << (isConvex(g)?1:0) << endl;
    return 0;
}