l=1,x=a,y=s
l=2,x=b,y=t
l=2,x=c,y=t
l=2,x=d,y=t
l=2,x=b,y=v
l=2,x=c,y=v
l=2,x=d,y=v
l=3,x=e,y=w
l=3,x=f,y=w
l=3,x=e,y=x
l=3,x=f,y=x
l=3,x=e,y=y
l=3,x=f,y=y
