($n,$m)=glob<>;
@a=sort map{
	/(.{7}) (.{7})/;
	"$2 $1"
}<>;

$c=0;
for(@a){
	@r=reverse sort@r;
	/(.{7}) (.{7})/;
	$o=$1;
	$i=$2;
	for$j(0..$n-1){
		if($r[$j]lt$i){
			$r[$j]=$o;
			++$c;
			last;
		}
	}
}
print $c;