sets = readlines
sets.each{|line|
    h,w = line.split.map(&:to_i)
    
    break if (h == 0) && (w == 0)
    
    h.times{|n|
        w.times{|m|
            if m == 0 || m % 2 == 0
                print '#' if n == 0 || n % 2 == 0
                print '.' unless n == 0 || n % 2 == 0
            else
                print '.'  if n == 0 || n % 2 == 0
                print '#'  unless n == 0 || n % 2 == 0
            end
        }
        puts #new line
    }
    puts #new line
}
