loop do
h,w=gets.split.map &:to_i
break if h==0 && w==0
n=1
h.times do
    if n%2==0
    puts ".#"*(w/2) if w%2==0
    puts ".#"*(w/2)+"." if w%2==1
    else
    puts "#."*(w/2) if w%2==0
    puts "#."*(w/2)+"#" if w%2==1     
    end
    n+=1
end
puts
end
