H,W = gets.split.map{|m|m.to_i}
P = $<.read.split("\n").map{|m|m.split('').map{|n|n.to_i}}
#H,W,P = 1,1,[1]

p 0 if P.flatten.inject(:+)==0

#puts "#{H} #{W}"
#P.each{|e|p e}
#puts '---'

memo = Array.new(H+2).map{Array.new(W+2, 0.0)}
#memo.each{|e|p e}

for y in 0..H+1
  for x in 0..W+1
    next if [*1..H].include?(y) and [*1..W].include?(x)
    #puts "x,y = #{x},#{y}"
    for k in 0..H-1
      for j in 0..W-1
        next if P[k][j] == 0
        #puts "j,k = #{j+1},#{k+1}"
        a = Math.sqrt( (x-(j+1))**2 + (y-(k+1))**2 )
        memo[y][x] += a
        #puts "memo[#{y}][#{x}] += Math.sqrt( (#{x}-#{j+1})**2 + (#{y}-#{k+1})**2 ) = #{a}"
      end
    end
    #puts ''
  end
end

#puts '---'
#memo.each{|e|p e}

puts memo.flatten.sort.uniq[1]