n = gets.to_i
arr = []
n.times { |i|
  s = gets
  raise unless s =~ /^(-1|(\d)+)( (-1|(\d)+))+$/
  s = s.split.map(&:to_i)
  arr << s
}
raise unless arr == arr.transpose
n.times { |i|
  raise unless arr[i][i] == -1
}