#include <bits/stdc++.h>

using namespace std;

struct Point {
    int x, y;
};

int main() {
//    freopen("convex.in", "r", stdin);
//    freopen("convex.out", "w", stdout);
    int n;
    cin >> n;
    vector<Point> points(n, {0, 0});
    long double x1, y1, x2, y2;

    for (int i = 0; i < n; i++) {
        cin >> points[i].x >> points[i].y;
    }

    for (int j = 0; j < n - 1; ++j) {
        x1 = points[j].x;
        y1 = points[j].y;
        x2 = points[j + 1].x;
        y2 = points[j + 1].y;
        long double A = -(y1 - y2);
        long double B = -(x2 - x1);
        long double C = -(x1 * y2 - x2 * y1);
        long double znak = A * x1 + B * y1 + C;
        for (int i = 0; i < n; ++i) {
            x2 = points[i].x;
            y2 = points[i].y;
            if (!((znak > 0 && A * x2 + B * y2 + C > 0) ||
                  (znak < 0 && A * x2 + B * y2 + C < 0))) {
                cout << "NO";
                return 0;
            }
        }
    }

    cout << "YES";

    return 0;
}