n=[]
while (a=gets)!=nil
    n<< a.split.map(&:to_i)
end
n.each{|e|
    exit if e[0]==e[1]&&e[0]==0
    now=0
    loop do
        case (now%2)
        when 0
            e[1].times{|i|print i.even?? "#":"."}
            puts;now+=1
        when 1
            e[1].times{|i|print i.even?? ".":"#"}
            puts;now+=1
        end
        if now==(e[0])
            puts;break    
        end
    end
}
