Five girls are standing in a ground at a certain distance. Rekha and Beena are 18 m apart from each other. Veena is standing somewhere in the mid of Rekha and Beena. Pinky is standing 5 m North to Rekha. Rekha is 12 m West to Veena. Yamini is standing 8 m South to Beena. What is the shortest distance between Pinky and Yamini?