Arthashastra
तस्य समन्ततो मण्डली भूता भूम्य् अनन्तरा अरि प्रकृतिः ॥
The king who is situated anywhere immediately on the circumference of the conqueror's territory is termed the enemy.
english translation
tasya samantato maNDalI bhUtA bhUmy anantarA ari prakRtiH ॥
hk transliteration by Sanscript