求助,这道题百思不得其解!

Seven small towns__h,i,j,k,l,m,n,are serviced by 3 roads _route1,route2,route3

route1 ends at n &l,and passes through m only

route2 starts at h ,then passes through l &i ,and ends back at h

route3 ends at n&k,and passes through j only

two towns are directly connected if a person can drive from one of the town to the other without passing throughout the town.