#!/bin/ruby
def on_line(n, a)
    x1, y1 = a[0]
    grad = nil
    a.each do |x2, y2|
        next if x1 == x2 && y1 == y2
        return "NO" if x1 != x2 && y1 != y2
        if grad == nil
            grad = x1 == x2 ? 1 : 0
        else
            new_grad = x1 == x2 ? 1 : 0
            return "NO" if new_grad != grad
        end
    end
    "YES"
end

n = gets.strip.to_i
a = Array.new(n)
(0...n).each do |i|
    a[i] = gets.split.map(&:to_i)
end
puts on_line(n, a)