#!perl -l @x=@ARGV;$i=shift;$z.=$x[$_%2]x$i,$i=substr$z.$x[1],$_+1,1for 0..567;print substr$z,0,pop
#!perl -l @x=@ARGV;$i=shift;for(0..500){$z.=$x[$_%2]x$i;$i=substr"$z$x[$_+1%2]",$_+1,1}print substr$z,0,pop