# Enter your code here. Read input from STDIN. Print output to STDOUT
t = gets.chomp.to_i
t.times do
  n = gets.chomp.to_i
  arr = []
  brr = []
  n.times do
    a, b = gets.chomp.split(" ").map &:to_i
    arr.push(a)
    brr.push(b)
  end
  arr.uniq!
  brr.uniq!
  if ((arr.length.to_i != 2) and (brr.length.to_i != 2))
   puts "NO"
  else
   puts "YES"
  end
end