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 {{{
#include <iostream>
#include <cassert>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cctype>
#include <cmath>
#include <ctime>
#include <queue>
#include <set>
#include <map>
#include <stack>
#include <string>
#include <bitset>
#include <vector>
#include <complex>
#include <algorithm>
using namespace std;
// }}}
// #define {{{
typedef long long ll;
typedef double db;
typedef pair<int,int> pii;
typedef vector<int> vi;
#define de(x) cout << #x << "=" << x << endl
#define rep(i,a,b) for(int i=a;i<(b);++i)
#define per(i,a,b) for(int i=(b)-1;i>=(a);--i)
#define all(x) (x).begin(),(x).end()
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define fi first
#define se second
// }}}

typedef ll T;
struct P{
    T x,y;
    P(){} P(T x,T y):x(x),y(y){}
    void read(){scanf("%lld%lld",&x,&y);}
    P operator - (const P&b) const {return P(x-b.x,y-b.y);}
    P operator + (const P&b) const {return P(x+b.x,y+b.y);}
    T operator * (const P&b) const {return x*b.x+y*b.y;}
    P operator * (const T&k) const {return P(x*k,y*k);}
    T operator ^ (const P&b) const {return x*b.y-y*b.x;}
};
typedef vector<P> polygon;
bool isconvex(polygon A){
    bool ok=1;int n=sz(A);
    rep(i,0,2) A.pb(A[i]);
    rep(i,0,n) ok&=((A[i+1]-A[i])^(A[i+2]-A[i]))>=0;
    return ok;
}

int main(){
    int n;scanf("%d",&n);
    polygon A;
    rep(i,0,n){
        P p;p.read();
        A.pb(p);
    }
    printf("%d\n",isconvex(A));
    return 0;
}