#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef long double LD;
typedef pair <int, int> pii;



#define cp const point &
struct point {
	LL x, y;
	point () {}
	point (LL xx, LL yy) { x = xx, y = yy; }
	point operator + (cp a) const { return {x + a.x, y + a.y}; }
	point operator - (cp a) const { return {x - a.x, y - a.y}; }
	bool operator < (cp a) const {
		return make_pair(x, y) < make_pair(a.x, a.y);
	}
};

LL det (point a, point b) {
	return a.x * b.y - b.x * a.y;
}

void work () {
	int n;
	cin >> n;
	vector <point> a;
	for (int i = 0; i < n; i++) {
		int x, y;
		cin >> x >> y;
		a.push_back({x, y});
	}
	if (det(a[1] - a[0], a[2] - a[0]) < 0) reverse(a.begin(), a.end());
	bool flag = true;
	for (int i = 2; i < n; i++) {
		flag &= det(a[i - 1] - a[0], a[i] - a[0]) > 0;
	}
	for (int i = 0; i < n; i++) {
		flag &= det(a[(i + 1) % n] - a[i], a[(i + 2) % n] - a[(i + 1) % n]) > 0;
	}
	puts (flag ? "Yes" : "No");
}

int main() {
	ios::sync_with_stdio(false); cin.tie(0);
	int T = 1;
	for (int ca = 1; ca <= T; ca ++)
		work();
}