arr=Array.new
while str=STDIN.gets
    lines=str.chomp.split.map{|v|v.to_i}
    break if lines[0]==0 && lines[1]==0
    arr.insert(arr.length,lines)
end
arr.each do | lines |
    row=0
    while(row<lines[0])
    col=0
    while(col<lines[1])
        ch = "."
        if (row+col)%2==0 then
                ch = "#"
        end
        printf ch
        col=col+1
    end
    printf "\n"
    row=row+1
    end
    printf "\n"
end