while (h,w = gets.split.collect{|item| item.to_i})
 
if h == 0 and w == 0
    break
end

for i in 1..h do
    for s in 1..w do
        if (i+s) % 2 ==0
            print "#"    
        else
            print "."
        end
    end
    puts "\n"     
end

puts "\n"　　　　

end
