Peggy delivers pizzas. She left the pizza parlor this evening and traveled 4 km east to deliver a pizza to the red house. Then she left the red house and traveled 8 km south to the blue house. Then she left the blue house and traveled 4 km west to the yellow house, she traveled 2 km north to the green house. She now wants to return to the pizza parlor. What is the shortest distance between the green house and the pizza parlor?