There are 7 places A, B, C, D, E, F and G in a town connected by various roads AB, AC, CD, DE, BF, EG and FG. A is 5 km south of B. A is 8 km west of C. C is 4 km north of D. D is 3 km east of E. F is 7 km west of B. F is 9 km north of G. A person travels from D to F through these roads. What is the distance covered by the person?