def get_mark(row, column)
    if row.odd? && column.odd? or row.even? && column.even?
        return '#'
    else
        return '.'
    end
end

loop do
    h,w = gets.split(' ').map(&:to_i)
    break if h==0 && w==0
    
    h.times do |row|
        s = ''
        w.times do |column|
            s += get_mark(row+1, column+1)
        end
        puts s
    end
    puts
end
