h, w = gets.split.map(&:to_i)
a = (1..h).map { gets.split.map(&:to_i) }
b = (1..h).map { Array.new(w) }
(0..h-1).each {|i| b[i][0] = 1 - a[i][0] }
(0..w-1).each {|j| b[0][j] = 1 - a[0][j] }
(1..h-1).each do |i|
  (1..w-1).each do |j|
    if a[i][j] == 1
      b[i][j] = 0
    else
      b[i][j] = [b[i-1][j-1], b[i-1][j], b[i][j-1]].min + 1
    end
  end
end
p b.map {|row| row.max }.max ** 2
