import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a=new int[n];
        int[] b=new int[n];
        for(int a0 = 0; a0 < n; a0++){
            int x = in.nextInt();
            int y = in.nextInt();
            
            a[a0]=x;
            b[a0]=y;
        }
        int count=0;
        for(int a0 = 2; a0 < n; a0++){
            int s = (b[a0] - b[a0-1]) * a[a0-2] + (a[a0-1] - a[a0]) * b[a0-2] + (a[a0] * b[a0-1] - a[a0-1] * b[a0]);
            if (s!=0)
                count++;
        }
        if(count==(n-3))
            System.out.println("YES");
        else
            System.out.println("NO");
    }
}